Somebody lost their dog in the highlands not long a go - on top of one of the Munros - 3 days later someone found him - behind a wire fence that he couldn't get through - a very lucky dog and owner.
Lots of posters put up in your area is good too - and don't worry if they get taken down - just keep putting them back up till he's found.
And don't lose heart - a friend of mine has been looking for her GSP since 6tth December - we reckon she was taken for breeding, so her pups may turn up soon - she's been due in season. We'll never stop searching.
Others have turned up days, weeks, months and even years later - I'm sure he'll appear soon.