I believe it has happened to me as well. Perhaps in error. One classic was a pair of shoes that I couldn't find elsewhere and when I got them, not only had they been returned previously, they had a "Zappos" receipt in the box. (The two companies are related and use the same warehouses, apparently.)
Yep, mistakes happen. Sometimes you can get lucky. I bought an HP printer that was a "refurbish" that was a couple months old and perfect, for half the price. I think it was simply returned, not refurbished at all...and had a great warranty from amazon in case it was less than stellar.