The window for Jason's disappearance is very, very small in time and in location, which is really what makes this case so baffling.
Timewise:
Sources report that he was last seen by a neighbor helping his younger brother pull trash cans up from the curb at 10:45 AM. For simplicity's sake, I am going to assume Jason set off to Benson Magnet High School from his house on Bedford Ave. at 10:45 AM on the dot. Mapquest indicates three possible routes he could have taken (assuming that he did not take a detour to visit someone, as has been suggested on this thread). Going straight down Bedford is 14 minutes; for a physically fit, healthy male, carrying clothing, it's reasonable to assume he would have arrived at school at 11 AM. Had he gone left on Pinkney as opposed to Bedford, he would have arrived maybe 3-5 minutes after 11 AM.
We know Jason's co-worker called the Jolkowski residence from Fazoli's (she did not own a cell phone, as far as I know) between 11:15 AM to 11:30 AM to inquire about his no-showing at the school. We also know Jason worked at the Fazoli's on Cass St. According to Mapquest, in a car, it would have taken the co-worker 11-12 minutes to get to Fazoli's from the school. I don't know if she went to the school from Fazoli's or her home, nor do I know when she arrived at the school and how long she waited for him. The earliest the co-worker could have called the residence is 11:15 AM, which means she would have left the school not having seen Jason at 11:03/11:04 AM. Assuming she waited at the school for two or three minutes, (possibly having arrived at 11 AM), this means that whatever happened to Jason must have happened between 10:45 and 11:00 AM.
This leaves, at the smallest, a fifteen-minute window for Jason's disappearance. The maximum is half an hour, but because other sources report that Jason and the co-worker agreed to meet at the school at 11 AM on the dot, I'm leaning towards fifteen minutes.
This is a very, very small window in time.
Location-wise:
I calculated the total distance in the "triangle" from Jason's house to Benson High School (factoring in all of the "reasonable" routes he could have taken (i.e. Bedford + Pinkney + N 50th) and eliminating overlaps) to be roughly 1.7 miles of road that whatever befell Jason could have occurred on. This is a very small distance that at a "normal" pace, for a physically fit 19-year-old man, could easily be done in under 30 minutes, and so it goes without saying that this whole area of road and roadside (not including residents' properties) could have been searched by LE and any construction projects halted/scoured.
This is a very, very small window in location.
Now, onto the more conjectural part of what could have happened.
I did not know Jason, and I know all too well how sorely misleading family assessments of mental health can be. But for me, it's these ridiculously small windows in time and location that reduce the likelihood of this being deliberate on Jason's part. Jason was a considerate person, and at the risk of sounding crass, I don't think he would have chosen to commit suicide or run away in a way that would waste a co-worker's time. Then again, Jason sounds like the kind of guy who might have had trouble saying "no" to his boss. He might have accepted the shift out of guilt or shyness/anxiety, and could very well have booked it. I do not think going to the CWS and blowing off work, regardless of how much he loved baseball, is consistent with his character whatsoever. I think it would have to be something more serious, like hurting himself or running away, that would drive him to let his boss and his co-workers down.
This leaves four possibilities: (1) that Jason was involved in a freak accident in the vicinity, unknown to anyone, (2) that Jason was involved in a multi-person accident, and that the other party panicked and covered it up, (3) that Jason was mugged/targeted in the neighborhood by someone he didn't know, (4) that Jason was targeted by someone he knew.
(1) Third likeliest. Considering how small the aforementioned "triangle" was, a freak accident, where no one knows what happened to him, and he fell into some manhole is just a hard sell after all these years. Unless the investigation was seriously botched from the start, I think it's safe to assume that the areas in these streets were searched from top to bottom and that all construction sites were vetted. I really don't see this being probable. Someone knows what happened here, and I don't think Jason will be found in the vicinity in a situation where he was not targeted by an individual.
(2) Possible, but seems the most unlikely. I can picture Jason getting hit by a car, and the parties involved panicking and removing him from the scene. However, this was a busy area of Omaha, in broad daylight, and Jason was a big guy. If they were so panicked, I do think they would have just hit and run and left Jason lying on the street.
(3) Possible. Second most likely. I do think muggers and predators can smell fear and vulnerability, and despite his height, Jason was not an intimidating person. If anything, he seemed naive and approachable. I do think he could have been jumped or coerced into a vehicle by someone he didn't know. But in any case, considering his size, it would have been a conspicuous struggle, and in a neighborhood like his where houses are close together, it's relatively safe to assume someone would have seen something.
There might not have been a struggle, however, if there was a weapon involved. Investigation-wise, I think (3) with a weapon is the least desirable outcome, considering how hard cases committed by "random" offenders are to solve. My guess would be that performing (3) with a weapon in a way that avoids a struggle and does not draw the attention of neighbors would require the skillset of someone with a criminal record for violent offenses, someone who would keep their composure and cool in jumping someone and getting them into a car. This/these individual(s) would have gotten Jason in the vehicle and driven off to who-knows-where with him. I think if (3) with a weapon is the case, that it will take someone with a conscience to come forward or someone who wasn't involved in the crime (an ex-spouse or friend or something) to have heard something to solve this.
(4) Possible. In addition to (3) with a weapon, most likely. Jason was targeted by someone he knew and had no reason to distrust. I've noticed a lot of people here implying that he might have had an inappropriate, one-sided relationship with an older man or some kind of secret (possibly one-sided) romance that his family didn't know about. While this is possible, I really don't think it has to be the case. I really lean towards an older, male neighbor, not necessarily on the SO registry, possibly married and with a family, who he and maybe even his family knew in passing offering him a quick ride to the school and incapacitating him. Something like "The Lovely Bones". I think he was then transported out of the "triangle" and was killed, either being buried where he was transported to, or brought back to the perpetrator's property and buried (this seems less likely to me, and I really don't think Jason is in the area anymore). I think we're inclined to trust our neighbors, and Jason seemed like an especially trusting person.
I think the investigation needs to comprehensively focus on (1) all individuals (likely SOs) and neighbors who were living in that area regardless of their past record and (2) individuals with criminal records for violent, theft-related, possibly weapons-related offenses who might have lived at a larger radius from Jason's neighborhood. I could see there being legal snafus and an inability to obtain warrants or whatever that would inhibit movement in this case.
Whatever happened, it goes without saying that it's been 20 years too long. I think about Jason every day and really hope that wherever he is, that he's at peace. May your family see you again someday, JJ. I'm sorry this happened to you, and I'll keep you and yours in my prayers.
To Jason.