As a last resort w.r.t. routing, a packet is sent to all hopCount=1 nodes in the peer list. The idea is "we dunnow what to do with it, let's pass it on to our neighbours". The peers will go through the same three stages, so sooner or later someone is bound to find a way to get to the addressed node.
Note that broadcasting really is a method of last resort. However, the idea is that if the node is finally reached (at a very high cost to the network), it will have an ant route back to the originating node a response packet can now follow. When the response packet arrives, the ant route has been built up in the opposite direction as well (think about it). So broadcasting is typically necessary only when two distant peers need to setup communication, after that ant routing kicks in and the network will hopefully self-select the most efficient path.
