. Plenty of gun stores purchase firearms from people and resell them, or sell on consignment. In theory (though not always in practice) they conduct a stolen gun check when they take the firearm into inventory. They perform a second check when the gun is transferred on a 4473.This is not true. Gun stores have never sold stolen firearms and the reason the antis wanted UBC's is to create a registry of private gun sales under the guise of preventing felons from buying guns thru private sales (felons get their guns thru straw purchases and theft). That is why they need the make model and serial number with the UBC, even though options have been presented to achieve the same goal (thru CHLs) without a registration.
If someone broke into my house while I was away for several weeks, and pawned the guns immediately, it is possible that they could sell the guns before they were reported stolen. The stolen gun check on the 4473 is an additional attempt to catch that kind of thing.
If you choose to believe that it is only so the government can track which guns are going where, that is your right. I will politely disagree. And I can absolutely promise you that plenty of gun stores have sold plenty of stolen firearms, knowingly and unknowingly. The only way a company can be sure they never deal in stolen property is to only deal in factory new firearms. Any time used guns come in, so does doubt.