Yubda, Depending on what version Limewire you have, the search function is already in place. I think the 4.13 versions were when this was enabled. I can't be 100% on what and when but I know in the later versions it's available.
Might be time to upgrade. Hope this helps.
Charly also has a good point. All of you're files should be alphabetized. If they are not and you want them to be, CLICK on NAME on bar above you're files.