If the weapon was ever reported stolen by serial number it is in the database.If it's never been registered law enforcement won't have any records to search.
Unlike a rifle, there is little forensically that can be done to trace the load to a particular gun.
Actually the FBI keeps records of stolen weapons.
It is called National Crime Information Center (NCIC)
Only law enforcement can access that data base.
Here is a link to the description of that data base:
http://www.fas.org/irp/agency/doj/fbi/is/ncic.htm
But as stated if the serial number was not reported then there will be no data. For those who choose not to record serial numbers, you have less chance of ever getting your weapon back if it gets stolen. When a perp gets popped with a gun the serial number is run and if it is stolen they will attempt to return it to the rightful owner after the perps trial is over and evidence can be released.