You might think you could walk into the store, give them your credit card, and they could bring up a list of your past transactions. But even though the industry has moved to automated point-of-sale machines, most retailers don't have good systems for looking up transactions.

Registers each keep a transaction log, in chronological order. If you come in with just what's on the credit card statement (day and amount) they're going to need to do an awkward amount of work to find the transaction. Specifically, they'll need to review that day's logs, register by register, manually scanning for a transaction of the right amount. Once they find it they can check that the credit card number matches, and print off a duplicate.

If you know what register you were at, and what time you made the purchase, it's much less work for them. It's very surprising to me that their computer systems don't support searching, but asking at three different stores it sounds like they generally don't. I'm not sure why?