I knew a FFL who did the gun show circut. (he retired) The whole drive truck/trailer with carts to haul dozens of rifles, ammo,etc to a different show each weekend.
IIRC he told me he set up, checked EVERY gun before show starts, then next morning he checks every gun again, (plus before handed to anyone) and finally checked before show opens on Sunday.
Show over he puts long guns into "socks" on cart, trailer, home, locked in garage (with alarm)... A long time customer drops over mid week to buy that rifle he had looked at week before. So they unlock garage, unlock trailer, find correct rifle, pull it out, and he checks action (by HABIT as he always does)
Wonder of wonders it has a live rd in chamber. He said he had other dealers tell him "it happened to them" but he said this was HIS GUN.
I have zero doubt people put live ammo in guns at shows in hopes of someone getting hurt....