Looking for Someone before 1950 - try Manteno State Hospital

It was a surprise to me to learn that a state Mental Health hospital, such as Manteno Mental Hospital, Kankakee County, IL were not mandated to keep records or archive inmate records or names before 1952. http://www.mantenostatehospital.com/genealogy.html

I am searching for our g-grandmother, Henrietta Lewin. She is in 1900 US Census, but can't find in the 1910, 1920, or 1930 census. She is on one of her son's obituary.

Sooooooooo, not for grandma, but suppose we wanted to find someone and they are in a mental institution. Has anyone run into this problem before? Has anyone search for mental hospital records ????

Last night, I found, and purchased online- a death certificate for Henrietta Lewin, age 62, that could be our relative. Soon, I will learn where she was when she died in 1942 - her death; and maybe a clue where she was from 1910 until 1942.