Does he go back and fill the card up at a teller's booth inside Wal-Mart or do they just do them at the checkout? Does he go to the same Wal-Mart every time or maybe most of the time?
Any chance he has repeatedly seen the same employee when he does that, like they might know or recognize him?
Yes, he usually goes to the same Walmart. I doubt that she would have recognized him because he doesn't drive much. A tank of gas will last him a while.
I don't know where he goes to get more money put on the card. I'll ask him, though. I'll also ask him to dig up old receipts (providing he still has them... I *think* he shreds stuff like that and since he no longer has to pay income tax, I can't think of any reason for him to save them.)