Use your computer's search to look for some of the file names...they should be still on your computer Or try looking in the old saving location of C:\Documents and Settings\your username\Shared.

The locations for saving & sharing have changed in the new versions of LW. In LW tools > options > saving & you can shange the location of your saved folder if you want to.
Tools > options > sharing is where you can add other folders (like your old saved folder) for sharing, or you can change the location of your shared folder.

If it turns out that your songs have been accidentally deleted & aren't on your computer or in the recycle bin, try the advice here about file recovery.
DELETING FILES FROM LIMEWIRE LIBRARY-DON"T! - File recovery advice!