Never mind that, it's also against the law in the UK for retailers to resell cosmetics. They should ALL be binned if they are returned, regardless of usage, you cannot take the risk. I used to work for MAC and anything that was returned went straight in a bin, seemed like such a waste, but that's just the way it is.
It does seem a waste. Can't they use them as testers? Or would that be a stupid question these days as somewhere down the line, some maniac is bound to have tampered with something.