Unless you're using the 4.13.0 Beta, you'll need a file recovery program to try & retrieve the files. Use your computer as little as possible in the meantime.
Have a look through the thread below for file recovery info
http://www.gnutellaforums.com/open-discussion-topics/49851-deleting-files-limewire-library-don-t-file-recovery-advice.html

Good luck