I don't get it.
I have lost my car...several times, by being to drunk to find it. I lost a wife to the mailman. I lost control of myself and had a premature ....whatever when I was 16. I lost my wallet at Disneyland. I lost every baseball bet I ever made for the last 20 years 'cuz I bet on the Orioles. I have even lost my Levis' in a cemetary one night......in 62 years of life, I have lost a lot of stuff.
But never, ever, no day, no way, have I EVER lost my rifle.
How do that happen?
I think you are a good guy for attempting to return it, but I would laugh my azz off when the guy comes to get it.