Guristas kestrel with diamond, but no pirate strongholds

I’ve just recently noticed that my ships were being attacked by those guristas kestrels, and read up on it says that they come from pirate strongholds, however when I check it at the agency it says unavailable. Another ISK sink in HS?

The Agency can be a little slow updating those.

If you want to be sure grab some combat probes and expanded probe launcher and scan for “Forward Observation Base”.

Nope, none could be found