Gift card purchases scare me, but I continue to make them because they can be accompanied by a nice bonus. I worry about employee theft of funds.
That happened to me with a McDonald's gift card. I went back to the restaurant and they were able to check the transaction history on the card and saw the funds added then taken off. Evidently the employee who sold me the card took the funds from it. I was a little suspicious when I picked the card at the register, funded the card right there, and the employee took the card with him and said he'd be back.
Hopefully for you, they can see the funding transaction and any use of the cards, or if not actually funded, a receipt can show that the cards were never funded.