If he has the receipt, there should be a computer trail back to the card id that he used. He should demand that Walmart freeze that card (probably too late but worth the shot) while things play out. He should also demand the card's transaction history and register video. It was a Walmart employee who perpetrated the fraud so Walmart should be the defendant in small claims court. And tell them never, ever get a debit card or a gift card, certainly not in large demoninations.
He tried to do that. There is a phone number on the card to call and an APP number (whatever that is.) He called and spoke to a woman at Murphy. She said the receipt does not have the last 4 digits (sounds like bull to me); thus she cannot kill 9999 cards to kill just one. While sympathetic, she said there wasn't anything she could do.
Ok, perhaps not a Walmart employee although the Murphy / Walmart relationship should be probed. But if there is separation, then the electronic commerce transfer from Walmart to Murphy might open this up to some state and even federal agencies.