I knew this would happen eventually.
I stopped for gas on my lunch hour. I used the pre-pay pump as I often do. I went in and pre-paid $40, came out and promptly left without putting the gas in my car!!
I realized it when I left work and, confused, saw that I had no gas.
Fortunately the same guy was still working at the Esso when I went back. He saw me come in, smiled and said “go get your gas”.