The DMV can run a gratis to show who's name the title is in, it will have all the address information, if he has not moved you could contact him, he will have to request a duplicate title. Touchy situation, need to have the bill of sale from when the guy you bought it from bought it and one for when you bought it. Might have to pay a penalty for not registering the vehicle in a timely manner. I know Georgia is a pain on title and tag work. Good luck.