Quoting Tosh, Michael J:
> This is controlled by get_bug_link, and you can change line 337 to
> check if it is CLOSED instead of if it is non-opened.
>

http://mxr.mozilla.org/mozilla/sourc...gzilla/Templat
e.pm#337

My mistake, that was for 3.2. below is the link to the 3.0 source:
http://mxr.mozilla.org/bugzilla3.0/s...emplate.pm#409