Secondly, do the Vargr know about the ship? I assume no, and if that's true, then I suspect the players can make a claim on the area with the miners, and "discover" the ship they know is already on the claim. If the area is claimed already, then the challenge becomes gaining control of that one Vargr's stake; it need not be a conflict with everyone.
I expect Vargr belters will not have centralized authority -- there will be a loose agreement for registering claims, mutual assistance, etc., but most asteroids/ships will be functionally independent, and if anyone gets testy, everyone agrees to form a posse, with the claim of the initiator being forfeit and auctioned off. Something like that. Everyone's trigger happy, but there are repercussions if you start anything.