I really hope he comes back again. I work at an animal sanctuary and we have had cats wander off never to see them again. I prefer knowing even if it is bad news.
Have you put up notices around the area with a good picture and description of him? I rehomed a cat a few days ago by noticing a poster in the nearby town. If he is not microchipped, you should try ringing local vets, animal sanctuaries, Cats Protection etc, just in case some well meaning person took him in.