My father made a pretty big mistake one day. We needed oil for the Waverunner we just bought for our lake house, and he sent me and my mother to the store. While we wrote down exactly what he wanted, it sounded like jibberish to us. All we knew was the name of the brand and that there was a letter and a number next to it, and it was different than the other combinations.
When we got to the store, they were out of the exact thing he wrote down. We went up to one of the workers and told him we needed Yamalube something-or-another oil. We must have written it down wrong because he thought we were nuts. After walking around for 30 minutes, we swallowed our pride and called him. He told us again and it turned out we were in front of it.