I stepped up to an ATM the other day, and discovered the fellow there before me had left his card in the machine. I ran out with it, but he had gone, so, after some deliberation, I put it in my wallet to take home and cut up, and completed my own transaction.
Two days later, I opened my wallet to get out my debit card, and found only the stranger’s there. I must have left mine behind in the same ATM.