You know, he is probably hiding somewhere close by, since he has only been gone 24 hours. Now's the time to spring into action.
Put a box on your porch with his blanket or a family member's unwashed T-shirt. Maybe a little food, fish if possible, it's smellier. I would blanket your immediate neighbourhood with posters carrying his picture and Have you seen our cat? and multiple copies of your phone number that people can tear off (I always swear I'll remember the number and hardly ever do). You could put 'reward' - it might help, although I wouldn't mention the amount. If you see your neighbours outside, tell them he's missing and give them a poster. If they have garages or sheds, ask them to check that he isn't trapped somewhere.
After dark tonight, when most people have gone inside, get out there with a flashlight, which picks up cats' eyes (unless it's wildlife
) and more food or treats, and walk around the neighbourhood calling and listening. He may meow when he hears your voice and be too scared to come all the way to you, so the listening part is important.
Good luck! Believe me, he's as worried about his situation as you are.