This question is put on-hold with me as the last voter. At that time no one posted an answer and I'm sure because I put a comment after that.
However, somehow there's an answer after it was put on-hold. I confirmed the time it was closed via revision history and the time the answer was posted. It was a 1-minute gap.
I've never encountered this, as in my experience someone who is writing an answer while the question is closed will get a notification bar stating the closed status, and even further receive an error when trying to post that answer.
Is this a bug?