I've never had an escape, but what I've heard from others is to look in warm places – by radiators or heating ducts (although I assume your heat is not running right now) or even appliances that have a pilot light like a gas stove or water heater. obviously any place that is dark and secure feeling. Tricks I've heard for getting them back if you can't find them would be to put a fresh killed, or nice hot frozen thawed rat in a temporary hide, a shoebox or something – also spread flour or corn starch on the floor and look for tracks in the morning. Good luck.