I wouldn't give up hope. Try looking around heaters too, or somewhere where he can get warm. I know it's kind of different, but I have a crawfish in a fish tank and he is a big guy. I noticed one day he was missing (since I hadn't seen him in about 2 days). Tore the tank apart and found nothing. Apparently he scaled the wall of the glass, got out of the tank and fell about 4 feet to the ground. Crawled all the way across my basement and some how managed to climb 8in high into a bucket of disgusting water (it catches the sweat off of our water tank so the water was all corroded and blue). A year later he is still alive and doing well. Bottom line - don't give up hope. Search the room he is in thoroughly, you know how well they can climb and hide. My guess would be he is probably still in that room. Keep us posted! Good luck!