An agent with the ATF says after the store closed, the trustees turned over 379 boxes of 4473 forms.
Those forms have information about the gun owner, guns they own and allows the ATF to trace firearms. If there are any more of those forms in the pile they are property of the ATF.
From the story....Damn, sounds like registry.
The bold is mine, and IMHO, you're exactly correct. It is a backdoor sort of registry.
I'm betting those are added to a database somewhere.