OH, I SO feel your pain. I lost 3k words not so long ago. (thread here: http://www.verlakay.com/boards/index.php?topic=63420.0
) It was, for the most part, unsalvageable.
BUT, my situation was different because it was a faulty save issue.
My first thought was the same as Mindy--did you try the undo button? If that doesn't work, maybe try some of the suggestions posted in my thread.
After my tragedy, I set Word to auto-save every 5 minutes, and create back up copies. I have to go through and delete the back up copies every so often because they pile up, but I feel tons better knowing they're there. (I also email myself my work to two email addresses when I'm done, but that wouldn't have helped here.)
I hope you can find your work. I know how heartbreaking it is.