I've done this a few(2-3) times over they years. I want crushed tomatoes in a can. I see them on the shelf and grab a can. Except it's not the can I was looking at, it's the can right next to it. Get home and find out I bought diced tomatoes instead. Ugh. Back to the store I go. I think the other time it was diced/crushed pineapple.
One time I was looking at the large pieces of meat in the display case. I look at the total price or maybe even the price per pound. I saw a whole tenderloin that had a low total price. I bought it. Got it home and saw that the label was for brisket. Brisket per pound is much less than filet. It got me thinking if it was indeed a mistake or maybe someone in the meat department was hooking up a friend. But instead of the friend finding the under priced food, I ended up getting it.