I understand that, Rich, and I DO give him credit for that. But I don't see that he understands mistake #1 here - taking UPS's word over a customers. Calling a customer a liar - or even deciding quietly that he is one - when there's NO documentation that the package was received, is NOT the right thing to do!
And he did the right thing in apolgizing for HIS remarks, but what about his employees treatment of a customer?
Better to know what you don't know than to think you know what you don't know.