You're only sharing and searching files within a set of hosts. This horizon is a portion of the entire Gnutella network. As your connections change to different hosts your horizon also varies.

Searching again over time helps you reach the host you're looking for if you didn't find it at first.

About forcing a search to particular hots, this thread about Gnutella on a LAN may help:
<http://www.gnutellaforums.com/showth...threadid=17628>