The answer to this problem is to stop it before it starts. A responsible dog hunter should not put his dogs down to hunt on a piece of property where there might be the chance they will track a hog or bay a hog on an adjoining property where they don't have hunting rights and have not talked to the other landowner about retrieval of dogs. Bad things can happen when your dogs are bayed up somewhere they don't belong.
This is a terrible thing that has happened, use it as a wake up call to make sure it doesn't happen to you. Get retrieval agreements with your neighbors and get some handle on your dogs, it could save their lives.
Sorry for your loss, I will help you in any way I can with the legal system.
I did not want to say what Paul said too early but he is exactly right. Hopefully something can be done within the law but stop the problem before it starts.
Every piece of land or ranch I hunt...I either call or go talk to all neighboring land owners. Explain what and how you are hunting. Talk about the possibility of having to retrieve the dog. In my area I have picked up many additional acres to hunt by doing this and minimizing the risk of someone harming your dog.
Good luck with this....please keep us informed on what you do.