Everyone has such good ideas.
One of my BPs escaped and ended up sliding into one of the heating vents and she ended up freezing in the basement.
But on a brighter note, I had another escapee BP who woke me and my boyfriend up in the middle of the night, slithering on a shelf and knocking down a glass candle holder!
I like what Iceman said; check a nook or cranny, and if he isn't there, block it up so he cant get in.