During s5b connections when no stream hosts are acceptable, Blather behaves as if it tried

[benlangfeld]

The spec states:

If the Target tries but is unable to connect to any of the StreamHosts and it does not wish to attempt a connection from its side, it MUST return an error to the Requester.

Blather will go ahead and send item-not-found even if it didn't try any connections (in one case because all were local IPs, which are discounted by default).