I checked into this because the same thing happened to me. Due to the inexperienced cashier, you didn't received the proper receipt for 1 hour guarantee that has the correct TC number to register your product right away.
However, you would not have known because I made several calls to the 1 hour guarantee hotline until I figured it out. I went back to the store an hour later and explained the situation and got the right tc number if you don't registed the product with the 1 hour guaranteed receipt they will have to refund your money that is the only option
Review about: Walmart Cashier.
Reason of review: Poor customer service.