All I can think of is that perhaps the people who've been uploading from you aren't sharing.... not really likely though, even if some aren't sharing you'd still expect a few to be. It's possible that all the people who've uploaded from you are offline at the times that you're searching but again... a bit unlikely?
Somebody else might know

I can find files uploaded from me... they appear with a ticked paper icon next to them, though of course I haven't downloaded them!!

Yeah I agree with you I find it unlikely especially when I was in the middle of chatting to some of them while searching for the file they uploaded.

I'm wondering if Limewire will let me search for my own files or maybe theres a block on that kind of thing?

I know what your thinking, your thinking why the hell would anyone want to search for their own songs anyway, well I just thought it would be more encouraging to see the songs I uploaded in the normal search list so that I know my songs are being shared around, and it will encourage me to share more cause most of them are rare gems of high quality too!

You won't be able to find your own shared files in a search, but there's no reason that files of yours that other people have downloaded won't appear. Unless the people who've downloaded them are offline (which you've said they're not) or aren't sharing them.

If you want, PM me with one of the song titles & I'll search.

Iv'e sent you a PM mate, feel free to share the files once you downloaded them