@Tiffany919 This is a scam that is often perpetrated in the UK with amazon cards so I assume it happens in the US as well.
Apparently scammers steal cards (which are worthless until activated at the till). They then use the cards to pay for something (not really sure how this bit works) and then put the cards back in the shop. Next they wait until someone buys the card and activates it at which point they use the money quickly before the purchaser can.
As such it feels like the shop is responsible.