I have a Great, Great Grandfather buried in the cemetery. I was able to find the location of his grave (unmarked) from a list in the Minnesota Historical Society. I would be happy to check for your ancestor.
Are you aware that there is a program giving headstones to the persons buried there (and in the other State Hospital Cemeteries). It is called "Remembering With Dignity".
Please email me directly at: email@example.com
if you have any questions or would like me to check at the Historical Society the next time I go.