This is a case that is not specifically addressed by Amazon's return policy. As is the case with any return, all they really care about is that the item number

This is a case that is not specifically addressed by Amazon's return policy. As is the case with any return, all they really care about is that the item number of the item being returned is the same as the item number on the order they are crediting. Consider the following scenario: I buy 2 widgets from Amazon, and 2 of the same model widgets from Best Buy. I line up all 4 widgets to test and find that 2 widgets are broken. I have no idea which store the broken widgets came from since they are all identical. I return them to Amazon because it is more convenient. It is quite possible that I returned the Best Buy widgets to Amazon.