If you exhaust all the money on a prepaid debit card and have no intention of refilling it, your tendency is probably to simply discard the piece of plastic and move on with your life. But you may want to hold on to that card for a while, lest you have to jump through hoops if you return the purchase.

The Cleveland Plain Dealer’s Money Matters column has the cautionary tale of a Best Buy shopper who received a rebate in the form of two $20 prepaid Visa cards, which she then used to pay for most of a $42.68 purchase at the electronics retailer.

Since the cards no longer had any value to her, the shopper got rid of them rather than continue to carry around seemingly worthless plastic.

The customer subsequently returned the purchase to Best Buy, but didn’t realize until later that her credit card had only been refunded the $2.68 she’d gone out-of-pocket for the transaction. The remaining $40 had been credited to the account numbers of the two prepaid cards she’d use to make the purchase.

Best Buy confirmed to Money Matters that the store’s policy is to refund purchases in whichever form they were originally made. The cashier should have instructed the customer to hold on to the cards in case she needed to return the item, but the retailer claims it’s likely the cashier in this case didn’t even notice the customer had used prepaid debit cards since the customer used a PIN pad rather than having the employee swipe the cards.

We question that logic, as the cashier should probably have noticed that the customer swiped three different cards at the PIN pad. Regardless…

After the customer noticed that the $40 had been refunded to cards she no longer had in her possession, Best Buy decided to provide her with a gift card for that amount. Of course, unlike prepaid debit cards she can only use that money at Best Buy.

Just let this be a lesson that even after you’ve exhausted a prepaid debit card, you’ll probably want to hold on to it — at least until the return window on all your purchases has closed.

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