Did you look in Users: Library: Mail and then the map that has your email address, click the icon inbox.mbox and look if it's still filled. When it's empty, you've deleted it during the accident and will never see it again. If the old stuff still is available, you might try to re-install mail and see if it picks it up again. To be sure make a copy of it somewhere else (desktop or so) so you'll be able to copy the content of that inbox to the new inbox.mbox that will appear in your library when you re-install Mail. Big chance you won't need it, but it might come handy.