So I have a few Shell $25 gift cards that I received as a promotion from Office Depot (They have these promotions that if you make a $125 purchase, you get a free $25 gift card). Because the Shell station near my house is usually 30 to 40 cents more than Costco, I save these Shell gift cards to use when we need gas and we aren't going near the Costco.
So on March 11, I used the Shell gift card to purchase $15 worth of gas, leaving the gift card with a $10 balance. The gift card was swiped at the pump and then given back to me by the attendant. When I went to use the remaining $10 today, it said it had no balance and when I called Shell, they said it had been used up at a shell station last week. At no time was the gift card out of my hand other than the 30 seconds when it was swiped in March. And the PIN wasn't even scratched off until today.
My guess is there was a skimmer at the gas station. I'm guessing skimming gift cards is very lucrative, since there is very little chance the police would get involved if a credit card is not involved.
My recommendation for anyone else who uses Shell physical gift cards or any gift card that needs to be swiped would be to use up the full balance at one time. (Unfortunately, Shell does not allow physical gift cards to be added to their app, the only way to use them is for them to be swiped.)