<Snipped quote by Zoldyck>
Well it's about time someone guessed it. But wait a minute... WRONG! Watch it, boy, you've only got two more guesses.
Ooh wait, it was the fourth door that opened so... Is somewhere in there?
Although that would be way to obvious.
The other thing I could think of was him being locked up in the mirror which is a coupletely mirrored dimension, like in the movie Mirrors.
Those are my guesses. If it's anything else then I wouldnt know how we would be able to find him... I'm probably missing something obvious...