What to do about non working carpet cleaner when I have no receipt?

I got a Bissell carpet cleaner as a gift from my dad for christmas and when I went to use it for the second time the water quit flowing the thing that spins on the top wasn't spinning. My dad cant find the receipt that you would need to take the product in somewhere for repair for warranty. The inside of the box and the paper inside says do not return to store... not sure what to do from here. He bought it at Walmart.