So I cleaned up the original and voted to close the duplicate. Unfortunately, he then proceeded to delete the question I just cleaned up. Annoyed, I told him he shouldn't have done that. And as a result he seems to have undeleted the original.
Now it does seem that the close votes have been reset. Either that, or I no longer have an indicator that the question currently has a close vote. Trying to vote once again shows me I can't do so because I already voted on the question.
Is this expected behaviour? Or are we dealing with a bug here?