Are you playing them in the Limewire player? go to your save folder (Limewire>tools>options>saving>save folder will give you the location) and The songs should be in there unless you have moved them. Try playing them with your audio player ... iTunes WinAmp for example or whatever you use. If the songs are no longer to be found, I'm wondering if you have managed to delete them.
See
http://gnutellaforums.com/showthread.php?t=49851
Let us know if this helps atall