I found this article in the archives of the Omaha World Herald. It's restricted access so I screenshotted it here. Basically it describes a possible sighting of Jason at a state park more than a week after he went missing. Normally I wouldn't consider that of any relevance, but one thing I did find interesting:
This state park is the same area where that human skull was found a few years ago. The skull was never identified, but was determined to be a white male aged 19-30. I uploaded a map of the state park where Jason was possibly seen vs. where the skull was (approximately) found in 2017. I've also linked the article about the skull.
Obviously it's all circumstantial, but I did find it interesting that there is at least one article out there about a Jason sighting after his disappearance. I know
@studebkr mentioned that people were confusing Jason's cousin for him, but here is at least one written record of one.
ETA: While I do not necessarily change my original opinions on the case, this opens the possibility of other options: if he was in the area after his intial disappearance, perhaps he drowned in the river and didn't resurface? Maybe he was killed there and dumped? Who knows.
Found skull reveals few clues so far