And he definately isn't in the cemetery (or that plot) with her? I was thinking of finding out through the cemetery, who has ownership of the grave. But in hindsight, I don't think that will help you out as it would seem John might have gone first, and one of her children might have organised her plot.
As for Water Police Records - I would hazard a guess that they might be out at State Records. Give them a call and they should be able to tell you.
Have you looked for him in asylum records as well?
Katharine.