Is he neutered? Some dogs lose their tags. If he is neutered, he might have a microchip.
Any vet clinic can scan him for free.
You could look through the craigslist lost and found section, and also
www.petfinder.com.
You might want to check the Orange County shelter, and maybe Durham or Wake too.
He could have been lost for awhile, or maybe escaped from a car, etc.
Go to
www.lostapet.org and look at their dog posters under the "recovery tips" section.
Under the same section, look at "I found a Stray Dog" has some good suggestions.
Placing some posters at a few intersections might get you a few tips.
Also, check the Bulletin Boards at grocery stores, etc.
It seems like someone should be looking for this guy if he has an invisible fence collar on....