I have a friend that found her cat stuck upside down behind her hot water heater in her small apartment, when she came home from work. If she'd found him any later, he would have died. He was not only traumatized, but severely dehydrated. In the past we've found our cat (Smokey) behind our clothes dryer. Fortunately for us, he's very loud and vocal when called. We've since made sure he can't get behind our washer and dryer set.