Really, really ironic that this thread pops up on the first "bad" day I've had in over a year.
I recently started a new job at Walgreens. For those outside of the US, Walgreens is the biggest pharmacy in the US, (and also a grocery store) and one of the biggest companies in the US...
I had a guy come in today around 9:00AM. He browsed the store for awhile and decided to buy some printer paper. He was around 20-25 years of age. I scanned the paper and the total was around $6.00. He gave me a $20 and while I was in the process of giving his change to him, he asked if I could give him 5 $1.00 for his $5.00. I said sure and proceeded to give him the 5 $1's.
In the back of my mind, I knew that this is an exact setup for a "quick-change trick." This guy wanted me to give him the 5 $1's and his 5 back by saying that I never gave him the change. He was a horrible "quick-change artist" because the money was still out and visible to him and I. The story ends with him losing the small argument and walking out with his paper and the correct amount of change.
Maybe not a bad day but if he had gotten away, it could have been a lot worse.