Chances are very high that he has a home and that someone is searching for him. Normally I'd say let him out, but if you have fireworks around where you are tonight then perhaps not, but do please get him scanned for a chip on Monday. If no chip, then a "found" ad in the local paper - and read the local paper regularly for "lost" ads too - and a poster or two in local shops. If none of those bring any result then after a week or two you can reasonably assume he is yours.

Liz