If foul play was involved, then the phone was probably tossed.
I do think that the apparent ringing of the phone months later can be explained by a busy tower bumping the call to a different tower. That happened right after the beginning of the semester, and towers near the campus would have been very, very busy indeed.
I still consider an accidental death and concealment in the construction area the leading theory, but a death or body dump in the river is the runner up. Many drowning victims are never found. If a drowning victim has a low percentage of body fat, as Brian appeared to, then it is more likely that the body will not rise to the surface.
I have often heard people make statements such as “if he was in the river his body would have turned up by now”, “he was nowhere near the river”, “he is never seen leaving the bar”...
The fact is, many people who have died in a body of water have never turned up and their bodies have not been recovered. There isn’t very much mystery about that. Water has currents, and any body of water can be dangerous and unpredictable no matter how shallow. Also, I’m not sure to what extent Olentangy River was searched. It’s not like the search began immediately. The river could have taken his body away by the time the search was even started! And Olentangy merges with Scioto River at Columbus. Scioto is much larger, and who knows, maybe Brian’s body ended up there... to me, it’s absurd that so many people just dismiss the fact he could have ended up in the river. To me, the chance of this is so much higher than any other theory since there is so little evidence and that Brian’s body hasn’t been found. And you are right, based on body composition, his body could have not been risen to the surface, although decomposition gases are also a factor that play a role in this... either way, his body could have been lost and carried away easily.
I would have considered death in the construction zone although this isn’t a theory I embrace readily, since there are so many factors involved that I’m not really aware of. How close and accessible was the construction area entrance to the bar attendees? What was the extent of the construction? My mind just can’t wrap itself around the fact that there would be a dead young man in the area and nobody would notice or smell anything? I know crazier things have happened and we cannot exclude this, but one would think Brian could have been located had he been trapped somewhere in the construction area...