EDIT: after further discussion with the other moderators, I have now undeleted your answer. Since you didn't VTC the question, there's no reason to believe you thought it was a duplicate when you answered; and since it now has 4 votes to reopen, its duplicate status isn't as clear as I'd originally thought. Apologies for the incorrect deletion.
Original answer follows.
Having noticed a large number of duplicate questions in the harry-potter tag recently, I spent a while browsing through them to see whether any of them had been answered, and sometimes taking appropriate action if so.
In some cases such as this one, where the two questions were exactly identical and the duplicate had an answer that would be useful as an answer to the older question, I merged the duplicate with the older question so that its answer(s) were transferred.
In other cases, such as the one you raise here, the answer to the duplicate wouldn't have fit well as an answer to the original question or wouldn't have added substantially to the existing answers there, so (after consultation with other moderators) I deleted the answer. This is in line with what @AncientSwordRage♦ said a while back about a similar case: "Bad questions get closed and don't get answers". Of course duplicate questions aren't necessarily bad, but the same principle applies to answerers: if a question is a duplicate, VTC it instead of answering it.1
You have not been targeted, nor was this about robbing you of your gold tag badge (which would have been a futile exercise anyway, since you could always post another HP answer and get it back).
1 As a general rule, this maxim has at least one exception on SFF: story-identification questions, which must have an answer confirmed in order to be closed as duplicate. But that's not what we're dealing with here.