I was hoping that Panther would add support for indexing of the junk mail folder (so that the search function would work on junk messages), but the product team has again decided to prevent it.
So for that once-a-week (for me, anyway) occurrence where the junk filter eats an email that isn't junk, I just changed the rule so that "junk" mail go into a new mail folder ("junque") that I created. This way, I can quickly find the lost mail without having to read about viagra and mortgage rates for 10 minutes.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20031110184205856