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.

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.

There seems to be a feature request to make this not happen, but apparently it is a sufficiently rare corner case that SE hasn't got around implementing it yet. See also this on meta.SE.