E-Z Mart complaint: Theft

When I went inside to get a drink and snacks for a road trip, a younger guy in training by an older thin woman was my cashier. I paid with debit card and they asked if I had a rewards card. I said no I don’t have it on me and the older woman told the boy to go ahead and scan one now and he reached over and grabbed a rewards card and scanned it. I said that’s not my reward card, who’s card are you scanning? She told me it’s a blank card to give me a discount. It then shut the system down so she told him this is why we usually only do it for cash payments. They had to cancel the whole transaction and start over and then he tried scanning the supposed blank card he pulled from the computer again not from the stack of new cards. It went through but as I was leaving I heard her say put a sticker on your card so you know it’s yours.