I have thunderbird "version 2.0.0.14 (20080501)", from the RPM thunderbird-2.0.0.14-1.fc10.i386. I have a "Sent Items" folder on an IMAP server. Every single message in the "Sent Items" folder comes from "Jonathan Kamens <jonathan.kamens>". There are currently 217 messages in the folder. When I select "Sender" in the quick search box, type "Jonathan", and hit Enter, only seven matches are displayed, rather than the expected 217. The same is true if I search for "Kamens" or "jonathan.kamens". I have tried opening the properties for the folder and rebuilding the index. This does not help. I have tried unsubscribing and resubscribing to the folder. This does not help. I have tried exiting and restarting thunderbird. This does not help. Beagle is able to see all of the messages in the folder, once I install beagle.xpi from the beagle build (which is missing from the beagle-thunderbird RPM, as noted in a different bug report), so this tells me that the search which isn't working isn't using beagle. Edit > Find > Search Messages is also able to see all of the messages in the folder, so whatever the problem is, it's limited to the quick search box.
We filed this bug in the upstream database (https://bugzilla.mozilla.org/show_bug.cgi?id=446578) and believe that it is more appropriate to let it be resolved upstream. Red Hat will continue to track the issue in the centralized upstream bug tracker, and will review any bug fixes that become available for consideration in future updates. Thank you for the bug report.