re: What's the worst you've ever messed up at work?

In college I worked a part-time job at a large corporate truck rental and leasing service. One of our clients, a large area food distributor, was having issues with the refrigeration unit at their plant, and needed to store some of their product in a spare refrigeration truck that we had. Due to the chaotic nature of the situation, they had to leave the fully packed truck on our lot overnight and come back to pick it up next day.

This job typically consisted of working with truckers and local businesses, but we would sometimes rent moving trucks to random weirdos who would come in with a fat stack of cash that we couldn't really reject on the basis of them being sketchy.

Anyway, as I'm about to close up on that day, a guy comes in begging for a truck that had a lift gate, as he needed it to move "some parts." Not being fully up-to-speed on the client's refrigeration situation, I tell him all we have is a refrigeration truck that has a lift gate. He drops $500 in cash on the counter, and I start the process of renting him the truck.

Where I really fricked up was being too lazy to fully inspect the truck I was renting him. I didn't really go out and check the truck, nor did I pay close attention to our computer system that it was marked as "unavailable." I guess I just really wanted to go home that day and assumed everything was fine. I go on and give him the keys to the truck that was storing about $15,000 in premium meats cuts, seafood, and frozen pizzas. The dude gets in, apparently not noticing the refrigeration engine is running and takes off. I close up and leave.

At about 4am the next day, I get a frantic call from my boss, asking me where our client's product and the truck are. That's when it hit me how badly I fricked up.

Welp, this dude definitely figured out what he was carrying in the truck, so he proceeded to empty it out and leave the truck on a random side street. Needless to say, the client was not happy, and the police had to go through the process of tracking this guy down, because he definitely didn't live in the address on his ID.

This all happened about a week before I was set to graduate and move to DC, so my boss figured it was pointless to fire me since I was mentally checked out already. I still feel bad about it, but I absolutely just went with, "Damn, that sucks. Welp, peace out and good luck." I moved away about 8 days later, leaving them with a very shitty situation.