The list in itunes is probably just a playlist and not the actual file. So transfering them from itunes to LW isn't going to work. Try searching you hdd for the files. The default location is C:\Documents and Settings\"your account name"\Shared.
If you can't find them, you'll need a file recovery program to try to get them back. See:
DELETING FILES FROM LIMEWIRE LIBRARY-DON"T! - File recovery advice!. If that doesn't work, then you'll have to redownload them
.