Cats sometimes go for long walks (or more than likely he has found somewhere nice to sleep!) My cat Cheeky very rarley spends more than a few hours away from the house (he likes his food and home comforts too much!) A few months ago he went missing for 2 1/2 days, I spent hours looking for him as did my neighbour. On the 3rd day I got home from work and he was sat asleep on his chair in the conservatory. I haven't got a clue where he went!
So I'm sure your cat will turn up soon. If he isn't back by tomorrow maybe knock on a few doors in your street, he could have accidentally got trapped in a garage or shed or something. I'm sure it will be OK eventually.