Panda Express

My 10 yr old grandson had surgery on Dec 5 and around that time my pastor's wife went to the Panda Express at Market Place Mall and purchased a $40 gift card. My grandson is in a wheelchair and went with his class from school on Friday, Dec 14, 2018 to the Panda Express and attempted to use his card. He was told the card wouldn't go thru the machine. I went to the Mall today, Dec 15, 2018 at 5:30pm and asked to speak to the manager on duty about the card. She first asked me where the card was purchased and I told her it was there at the Mall. She said they don't put the amount on the front of the card like it was on the card I had. She tried to use it in the machine and she said it was not in their system. Had it been $10 I would have let it go but with it being $40, I was not happy with her response. I did not have the receipt because it was with the card when my grandson got it but apparently he misplaced it. Surely there is some way that a gift card for this amount could be tracked. Is there any recourse to this problem? I am wondering if someone took the money and did not activate the card.