Hidden, to me, = prisoner. So I can't see this as a viable option, by anyone known to him and professing to care about him. He would have to either be restrained so as not to escape, or kept watch over like an inmate. He has missed weeks of school, the holiday season as well as Thanksgiving, and who knows what else. I have no confidence in this being an option at all, unless someone is severely deranged. I imagine LE would have checked out all relatives and close friends of the family early on, at least one would hope so, and that no one is unaccounted for. Going on two months is a long time for anyone to be absent without anyone noticing. And it would likely have to involve more than one person, in order to prevent escape.
Very unlikely scenario.