"Obviously the hypothetical thug was going to turn in the gun he 'found', but he hadn't had a chance to by the time he was caught...."
Obviously that excuse wouldn't fly for people with common sense.
"Why do you think the NRA is wrong to say kids shouldn't pick up and carry guns they find?"
Depends on the kid. This one had the knowledge to keep it cracked open so it wouldn't fire, I don't think he was a danger to himself or others.
But not enough knowledge to tell it was not a real gun.