It’s becoming an organized crime tactic:
> Card draining is when criminals remove gift cards from a store display, open
> them in a separate location, and either record the card numbers and PINs or
> replace them with a new barcode. The crooks then repair the packaging, return
> to a store and place the cards back on a rack. When a customer unwittingly
> selects and loads money onto a tampered card, the criminal is able to access
> the card online and steal the balance.
>
> […]
>
> In card draining, the runners assist with removing, tampering and restocking
> of gift cards, according to court documents and investigators...