Have you used the computer's search to try & find them? Look for one of the file names & see if they turn up somewhere. Is it possible that you (or maybe somebody else) deleted them by mistake? Delete from the LW library is hard to get around, things don't go to the recycle bin. You'd need a file recovery program to try & retrieve them
http://www.gnutellaforums.com/showthread.php?t=49851

Good luck