I recently answered a really old (unanswered) question with a quite extensive answer, and today, when I logged in, I was greeted with "You have been awarded the Necromancer badge". My Badge page also shows that it is for this answer - but it only got 4 up-votes until now (no down-vote).
(I also got three other badges at the same time, but these are clear).
How can this be? Did someone vote for my answer and removed the vote immediately again? Or did I misunderstood this, and it requires 5 votes on the question, not my answer? If so, this should be made clearer in the description of the badge.