Yes, if you close, all your 4473's in the past 20 years must be turned in. But, federal law still prohibits the ATF from putting them in a searchable database so they are literally stored in storage containers. So if the ATF wants to know exactly how many guns John Jacob Smith has had transferred to him on a 4473 they will still need to physically check every FFL in the country plus finger through the hundreds of thousands they have stored from closed businesses. It would be a seemingly impossible task.
Apparently.
I had one of the few new guns I've ever purchased new, stolen. Had the receipt from the FFL, knew the exact date of sale. But needed the serial number from the gun (another long story).
My bad luck is that the FFL had lost it's license in the ensuing years, and yes, the 4473s go back to BATF. Apparently they store them in the warehouse you see in the last scene in Indiana Jones, because despite several requests from the local LEO, BATF couldn't (or wouldn't) find the 4473 (which I needed for the serial number). Since that experience I haven't obsessed over the BATF having that info. I'm not planning a mass murder, which seems to be about the only time BATF goes to the trouble.
Here's the P.S., the physical location of the FFL had stayed the same and continuously operating, but the actual FFL was in a different name. I knew that it had happened, but hadn't made the connection that all the 4473s had gone north somewhere.