Usually the store blames the new purchaser for trying to scam the store. Maybe they tracked the individual serial number at the time of purchase and original return instead of just scanning the UPC so they knew this one had been purchased and returned previously.
Happened to us at a Walmart in Naples, Florida. Bought a new Nintendo DS. Walked out of the store and openned it in the car. Found that it was replaced with a worn out previous model. Even the cord was old.
They were very nice about giving us our money back.
Shrink wrap machines are apparently very common in the USA!