If your songs are in the WMP library (not just m3u playlist files, but the mp3 files) then you should be able to move them back into your shared folder.
Have you had a look in your LW saved folder (remember you can have a saved folder, for saving downloads, as well as different folders being shared)?

If all you can find are playlist (m3u) files, your mp3 files might have been deleted by mistake? If it turns out that you have deleted them (it happens), see the thread below for some file recovery advice
http://www.gnutellaforums.com/showthread.php?t=49851

you beat me Grandpa! And yes, I know there's a line under this text but I can't get rid of it!!!!