I, too, have had babies escape their boxes and was lucky enough to find them within a few hours of searching. Twice, I found them on a curtain rod in the corner of the room above a window! Don't ask me how they got up there, but both of them went to the same location on separate incidents. Weird. So... Don't forget to look UP in your searches. They can and DO climb.
Good luck - he'll show up. I was paniced at first too.
Andy-![]()