Astraea
Richard, I just remembered another weird incident with Amazon where they told me to keep the merchandise.
I received a package addressed to me - name, address, everything was correct - but it contained two items I had not ordered and would never have wanted. After several back-and-forth emails concerning number codes on the label, they figured out where the mistake had arisen. I asked them to issue a return label so that the right person could receive the order - but Amazon told me to keep the items. I didn't want them and said so, but Amazon replied that they hoped I'd find a use for them and enjoy them! So I really think you're fine to take Amazon at their word, as they've already told you not to return the deck.
I received a package addressed to me - name, address, everything was correct - but it contained two items I had not ordered and would never have wanted. After several back-and-forth emails concerning number codes on the label, they figured out where the mistake had arisen. I asked them to issue a return label so that the right person could receive the order - but Amazon told me to keep the items. I didn't want them and said so, but Amazon replied that they hoped I'd find a use for them and enjoy them! So I really think you're fine to take Amazon at their word, as they've already told you not to return the deck.