I've heard of people with BP's that can climb door frames. It's easy to underestimate them. Don't for a second think that you'll have to find them down load.
Quite the opposite actually, a lot of times they can get up easier than they can get down. Their only way down tends to be falling, in which case you'll probably hear him.
Ooooh boy.
That puts a whole new spin on things.
The good news in your post is, that if my worst fears are true and he's fallen down into the wall somewhere, he could conceivably get back up again.