This really has nothing to do with morals. If this person was giving up his right to roll on what he really wanted to help out a friend, I see no problem with that. It's not like a seal came up and he decided to switch after he knew the seal was already up. I don't know why they would have felt like they needed to do the exchange in private, but still nothing unethical about this situation. As has already been stated, your chances to get the drop didn't change just because another persons chance to win increased. I have a feeling that you are more upset about letting the guy who won the seal change what we was lotting for to seals. Next time just don't let someone change mid party.