In my situation, I purchased the gun from a licensed dealer, did the 4473 thing, etc. According to the agent, who was very nice, when the firearm was found, a trace was started by going up the string from beginning of its life, ultimately to the store/dealer that sold it to me. I was the last link in the string of documentation. The only documentation I had was my record of items I had bought and sold over many years. I told the agent that the date, and location of the show, was the only information I had, and he was completely satisfied with that, thanked me, and that was the last I heard.
Most gun folks seem to be known for the part of the hobby that involves the buying, trading, and selling of their collections, and this agent told me that unless we have some other issues with law enforcement, they pretty much take our word on our activities.
