The reason this happens is because your computer/device doesn't reload the page while you are answering. If it did, it would clear the text that you would have put in the answer box. Because of this, there really would be no way for you to be updated of such a thing. Yeah, it sucks, I know. I've had it happen to me a couple times too, and it's dreadfully annoying, but unfortunately there isn't much that can be done about it :/