So if I get a knock on the door, I'm more than happy to show the official my log book to confirm we are indeed talking about the same firearm and that I sold it on a certain date. I'm willing to help with the investigation as much as I am able.
I wouldn't show them the log, just say "that gun was sold." I also wouldn't offer extra help to any investigator freely without a lawyer. Who knows how they could turn your log against you if they felt the need. *Puts tinfoil hat back on