I guess I disagree and agree, LOL! Seriously guys, I have batted this damn thing back and forth for a few years now, as I'm sure many others here have as well. Why, because there's virtually no evidence of anything, which leads us all to nothing else but inconclusive.
It's no doubt a true mystery, maybe one of the biggest ones in our time. That of course is if you discount Bigfoot or Aliens.
Honestly, At this point, I am leaning toward him making it out of the building. After that, it's up for grabs. Either he left on his own and started a new life, or he ran into foul play.
As far as his phone, well, it could have been him. I agree he could have hidden out there for a while before leaving the area. Not hard to believe at all, If you have what you consider to be a toxic family, perhaps you aren't really close to them.... who may not agree with your life choices, etc., and if you feel the need to distance yourself, then that's what you might do.
Believe me, I've been there, and actually regret not doing what "that person" might have done. Talk about freedom, what a relief.
On the other hand, it could have been a killer who ended up with his phone. Or, someone who found his phone and.....