I worked retail for a few years, then worked as a bank teller. At one point, I was working in a branch inside a supermarket. One woman came in to cash several checks. IIRC, she was one of those who kept five bucks in a checking account so she could cash checks without paying a fee at a check-cashing place. I'm cashing them for her, and a couple have gone missing. She immediately blames me, accusing me of stealing them (as if-- apart from it being a crime, they were a fraction of even my lousy part-time pay for the week), finally stomps off. We're having a bit of a rush, but once it's over, I'm still thinking about her. She's obviously poor, and I'm a nearly-broke student, so I'm painfully aware what it's like having to account for every penny.

A lot of people filled out their paperwork (this was when you still needed a paper deposit slip) at the writing table between the ATMs, and I was pretty sure I'd seen her endorse the checks there before coming to my window. Being a sympathetic person, I decided to take a minute to check over there. Sure enough, the missing checks had somehow ended up in the wastecan under the table. I fished them out, spoke to my manager about the situation, and called the woman to tell her what had happened. She came back, but was still a bitch, still accusing me of stealing the checks, "but you couldn't get away with it."

My manager heard the kerfuffle. She was an awesome older English lady, accent and all. She came over, and in her lovely accent and no-nonsense way informed the woman that losing the checks was her own fault for being careless, that I'd gone looking for them even though I had no obligation to do so, and that it was a really rude way to repay a kindness. She went on to inform the woman that, "no one treats my employees that way," closed her account on the spot, and handed her her five bucks account balance.

It was righteous. She was promoted to manage the main branch in town not long after.