I keep reading on here that SLED has a registry. I wish someone would clarify this. From my experience when you buy a firearm from a dealer, the dealer calls into SLED for the background check. I have personally witnessed this and at no time does the dealer inform SLED of the specific weapon you are buying. All SLED knows is who you are, and whether you are looking to buy a pistol or rifle, and that is all. They don't even know if you actually purchased the gun.
The dealer keeps the forms you filled out until he goes out of business, and then those forms are sent into ATF and they are not allowed to use those forms as a data base, they are stored in their original condition.
All SLED is supposed to know is you were applying to purchase a gun, not that you did, and certainly not the specific weapon you purchased.
If SLED came to your buddy, the path I thought they would have to take (if no one told them they got the gun from him) is to go to the manufacturer, they give the distributor, who gives them the dealer the gun was sent to. That dealer then goes through the records he is supposed to keep to find out who originally purchased the gun.
If I am mistaken, I would appreciate someone letting me know the exact process. I do not trust the government now or for what they may do in the future, and agreeing to a database now (protected by court order) is just a single bill in Congress from making those records an open guide map for how ever they want to use it.