One scammer I encountered years back at Fal-Mart, a couple were returning a brand new bike. Even had the receipt. The only thing wrong with this was the barcode sticker and the big round card that is inserted within the spokes on the front tire were for a completely different bike.
They were returning one bike that cost about $150 (I believe the brand was N.E.X.T.), but the receipt, barcode and display card were for I believe a Schwinn bike that was about $200.
I wouldn't authorize the return, as they were completely different brands, along with the significant difference in price. They tried to tell me that was how they purchased the bike. I informed them that it wasn't possible, as the barcode and display card are not placed onto the bikes by Fal-Mart assemblers. The bikes come that way from the vendor. And Schwinn would not have cards and barcodes for another brand bike.
They demanded to see a manager, and I was fortunate to have a manager call front desk before arriving. I was able to explain the situation before he arrived. When I left the front desk, I took the display card from the bike, and discarded it on my way back to toy dept.
The manager offered to return the bike, but not for the (incorrect) receipt price, but for the actual price of the bike. They refused, and took the bike with them, but not before demanding the display card back. My manager had me retrieve it and return it to them.
I did, however, call the 2 nearest stores to relay the incident so they would be on their guard.