The new LimeWire ultrapeers stop the search once they have returned 80 results (50 if you are using an older version of LimeWire). Maybe your friend's search wasn't specific enough - or the distance between the ultrapeers you and your friend connected to is too big to be crossed by a search. (If your messages have to cross 5 or 6 ultrapeers before they reach your friend, you will never find a file from each other).

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Morgens ess ich Cornflakes und abends ess ich Brot
Und wenn ich lang genug gelebt hab, dann sterb ich und bin tot

--Fischmob