archive folders have vanished

[Hadron Quark]

I have had my archived groups in my gnus folder list for weeks. They
have now vanished.

I found this thread which mentioned using "F" (find new groups) to
repopulate the group buffer but still my archives dont appear

http://tinyurl.com/n9p8w

I have this in my .gnus.el 

(setq gnus-message-archive-group
      '((if (message-news-p)
            "misc-news"
          (concat "mail." (format-time-string
                           "%Y-%m" (current-time))))))


and they used to be visible. Any ideas?

There is an archive/mail directory with my "monthly" archives under my
top level Mail dir.