Tennessee doesn't have registration. Only 5 states or so have registration of handguns, and a couple others have a quasi-registration/transfer recording.
Sometimes guns will end up in databases due to many reasons. Like used in a crime, reported stolen/lost/missing, etc. It doesn't take long for LEO's to run a firearm. Quick call to manufacture/importer, then to distributer, then to dealer for the 4473 recipient. It can be done in as little as 5-10min in ideal conditions.