Contact any pounds, shelters, rescues, city hall, vets, and police departments in the area he was lost as well as in towns immediately surrounding. Go to every shelter and pound personally to see for yourself if he's been picked up. Get as many "lost" posters up as soon as you can. You can place these on lamp posts, mail boxes, bus booths, depanneur windows, where ever there are bank guichets etc. You want as much exposure as possible. If you need a more detailed list of the places to call/visit, just ask.
Hope he's found and returned home soon.
Edited to add, the number you listed looks like a South Shore # . Did you make an error?