In the coming weeks, some retailers will be offering deals on unsold stock of popular holiday gift items. Sometimes stores are up-front about whether or not a particular product was previously purchased and returned, while many just put these items back into inventory with the truly new stuff. That’s why you need to open up those boxes before you leave the store — or else risk getting home to find you’ve purchased a box of rocks.

We’ve shown you many, many examples of shoppers finding out their new electronics purchase was actually a doctored-up floor tile, a bunch of useless notepads, or just some fishing gear.

The latest incident involves a Denver-area man who thought he was buying a PlayStation 4 from Walmart, only to discover when he opened the box that he’d paid hundreds of dollars for a box of taped-up rocks.

In this case, the man says that the Walmart employee who pulled the box from the locked shelf told him that the PS4 had been returned by another customer.

His attempts to get Walmart to give a damn hit the usual wall experienced by victims of this scam.

A manager at the store he’d bought the box-o-rocks from told him there was nothing that could be done because there was no way to prove that the box didn’t contain a PS4 when he left the store.

Eventually, the store decided to believe his story, refunding the customer his money.

We definitely understand Walmart’s hesitance to issue refunds to every person who claims they bought a box of junk. After all, it would be incredibly easy for scammers to pull such a ruse and score free products.

That’s why — as awkward as it may be — it is always best to check that your expensive purchase is actually inside the box before you leave the store. That’s the only way you’re going to be able to convincingly demonstrate that you are not trying to pull one over on the store.

Retailers should also stop this practice of immediately re-shelving returned items just because they are still shrink-wrapped. Any industrious scammer knows how to do a decent job of faking a factory-sealed product, so anything returned to a store should be inspected and marked as “previously owned.”

Want more consumer news? Visit our parent organization, Consumer Reports, for the latest on scams, recalls, and other consumer issues.