Older versions of Limewire used to say "Couldn't download" and simply stop. This is essentially the same, but searches are now automatically sent out periodically to find the file. Sometimes, it even works.

If you do a search yourself, Limewire will grab the file from the search hits. If it is a popular file, an additional search may yield a swarmed download.

You can increase your chances:

1) by maxing out your number of connections before doing searches and making sure that the majority of them are Limewire ultrapeers, not Morpheus and especially not Gnucleus.

2) limiting the scope of your Limewire session to a few categories where you can do more global searches (by genre or artist or whatever) that may grab a few of those requeries at once.