all of the sent messages in my windows live mail just disappeared in the middle of the day. where did they go?

I went to search for a previous email to a contact and when i clicked on my "sent" folder, only about a half dozen emails from several months ago popped up.  I searched earlier in the day, and everything was there.  It syncs from my gmail account and they are all in the gmail but I don't like using it and my contacts are all set up in windows live mail.  How do I regain my sent messages?