I will never understand how a company isn’t able to say a simple “sorry, we got it wrong”.

That whole thing could have been prevented if that Brock guy hadn’t tried to act tough and cross his arms trying to scare him. He could have said “This is hard, I’m not aware of this, but obviously you have a contract here. I’ll show you I have the inventory, and tell you what going forward I’ll keep a special note when anything is sold, but it’s obvious we aren’t going to be able to solve this just the two of us here. Let me contact the previous owner and see if we can figure this out.”