I've never heard that term "fail to download" in LW before. The reason LW won't implement such a feature is this Requeries (click on link) which is not good for the network. That's why the gnutella network does not get heavily queued up like the winmx one did.

So what's wrong with manually re-searching the topic & using different terms & techniques of finding such rare files? That's what I do because most files I seek are rare.