Same thing happened to me with a 1933 Goudey Ruth. Wow, that would have been a bad day if that really would have happened.
Honestly, I think the dumbest thing I've done to a card was when I was removing a T201 Johnson/Street card from a screw down holder and I didn't completely let one of the screws loose. I pulled on the card and guess what didn't come out of the holder with the card - yup, the corner... went from about a "5" to a "1" in a split second.
