The ATF directly has no records of what you bought.
When you buy a gun from a dealer, you complete a form 4473. Dealer conducts a background check over the phone/ computer with the Feds or in my case, the state. They get your identifying info, and the TYPE of gun (rifle, shotgun, other). At no point does the background check system say "Bobby Jo earl is buying a Remchester model 2 in caliber .800 Wowzer, serial number 1234.
The 4473 is retained BY THE DEALER for 20 years. During an audit, they ARE checked by the ATF for proper use, and that the inventory OUT matches what is on the 4473.
The ATF is prohibited by law from creating or maintaining a master data base of gun owners, and has no funding for a mega-million $$$ task like that.
PS- Regarding what you were "told" about the ATF- I was told Oswald acted alone, artificial sweeteners were safe, and Angelina Jolie married for love. You believe that?