I recently looked at an old question of mine (well, old, but the answer & discussion this refers to happened less than 2 years ago.) After a long discussion with the answerer in the comments, I had followed the automated suggestion "Let us continue this discussion in chat", and IIRC, we did. But this link is broken now ("Page not found"). Why?
That room was deleted, since it contained less than 15 messages, see this FAQ. I used my chat superpowers to undelete it, although it is bizarre that this happens for rooms created from comments. I've added two messages, so that this won't happen again.