I'd heard similar stories of customers buying goods they knew they only needed temporally that they simply returned afterwards and obtained a full refund for. It does surprise me a little that stores don't have mechanisms in place to prevent this being abused, it's hard to see how it couldn't be a significant financial drain for them.
FWIW "no questions asked returns" aren't really a thing in Australia from what I've observed. But not having a receipt isn't usually an issue if they can find the payment on their system and it matches your CC# either.