Most definitely have forgotten about different guns. None of my rifles or shotguns are "High Dollar" stuff, but they are fun to shoot.
I just bought another Stevens .22 Lr/.410 gauge over and under. My wife is the one who actually remembered I already had one just like it. We checked the various safes and gun cabinets and could not find another one. Then yesterday she found it in the barn. She also found a .22 LR and a 12 gauge shotgun I had forgotten about.
I remember running my trap line, when I was a kid, and carrying one of the .22/.410's.