It seems that i hold the minority opinion on this issue.
^^^ Would you guys look at a garage sale much differently than a gun show? It's a publicly announced sale, with deputies at the door, but i am not familiar with any sort of validation process that sellers are required to undergo to participate.
I've bought one firearm without going through an FFL; it was a reasonably priced rifle at a gun show, from an individual's collection. Dude had a table full & seemed to be accepted as a "regular" by the nearby sellers. Dude also copied my ID for his file & asked if i was prohibited from buying firearms, IIRC. I'm comfortable with that situation. I bought some ammo & magazines as well; should i have gotten a bill of sale on the mags as "gun parts"?
Honestly, if it turned out that rifle were stolen, i would try to get it returned to the rightful owner, and would provide all the information i have on the person who sold it to me (date from visa receipt for same day ammo purchase, physical description, and booth location).