The best way is to post details about the phone as a lost-and-found item in, say, the notice board at your local 7-11... Who knows, the owner may also be a local fellow and will be able to contact you should he head to that particular 7-11 and see the notice (the world is pretty small nowadays)?

Of course another way is to post on FB or even here on LYN, and let people spread the word around!