Not too many decades ago, even in venues like CA, people bought and sold guns at swap meets, to neighbors, friends etc, and there was little or no documentation. It was just no big deal. Doing that today I would imagine the offender would be thrown in a cage. I remember as a kid my Dads uncle came down from Alaska to LA to visit. He hadn't seen his uncle in 20 years. He handed my Dad a brand new S&W .44 magnum saying it's yours, the price was a steal! lol. After dad died the S&W was nowhere to be found, unfortunately. Mom could have gave it to one of his buddies...I dunno.
Thinking out loud, there must be tons of guns out there with unknown histories owned by unsuspecting people, where it's been handed down, passed around over the decades, lost, found, stolen, whatever.
I have never understood the difference between buying a gun and giving or selling it to someone else and a ‘sraw purchase’.
Feels like the only difference is intent, but how do they know what you’re thinking when you do it?