Technically your question says it was near 2 months since the last person posted in it.
I think you mean, this though: "Have you ever posted in a topic that had no replies for at least 2 months or more?"
Yes. On a forum that visit where people are a lot more mature, I did look into the oldest topics (which is now about 11 years old) which was at the time about 7 years old. I posted in that topic as if it was a new topic, just to prank the others. We didn't have a rule there about necromancy, so it was perfectly fine. But I wouldn't do it anymore today though.
Have you ever said something (or at least wanted to) to someone because you thought they were talking to you while they were actually talking to the person somewhere behind you?