I'm a lurker coming out of hiding ...
I've been reading for several days, although I didn't read the early threads so forgive me if this has been stated already.
There's been some discussion about his keys being taken away, by whom and that his mother told them to give them back. There's been a LOT of discussion about his mental status at that point.
I find it very odd that a girlfriend and/or roommate would take away someones keys unless they were threatening to harm themselves or someone else or if they were under the influence. I think the fact that he called his mother (I assume that's how she found out about them having his keys???) and she told them to give them back, tells a lot about his mental status. As a mother, albeit to an 18 month old son, I can see how your instincts to protect your child would kick in. If she knew something wasn't right and the fact that they took his keys was causing more stress to him (therefor possibly making him more "unstable" for lack of a better description), it's possible that she told them to give the keys back to reduce his "panic" (again for lack of a better word). She may have felt he would go back to his apartment and settle down and they could have a conversation. She offered to fly up there ... to me that's a mom that's worried about her child.
What's disturbing to me is the timeline ... if he had called and was freaking out about his keys being taken away, why was there no conversation between mom and son in the time he was driving (and yes, I know she was attempting to contact him, but from what I've gathered that wasn't until Thursday when she received the survey from AAA and realized he wasn't at school). If you were worried enough that you were offering to fly up there, why weren't they in contact on Wednesday? Or were they and I've just missed all that.
As to what happened to him ... I go back and forth on a lot of theories and a lot of that depends on the days leading up to it.
I fully respect the families privacy and a lot of this is none of our business. The fact is he's still out there, somewhere. However, knowing his "state of mind" might help determine where he's at.
I hope they find him soon. That family needs to know where their son is.