Where ARE you, John Bowman?

I cannot find John Bowman anywhere after 1930. These are the things I know: he was married to Emma F Turner. They were married in Fremont, Tuscola County, Michigan in 1879 (Michigan, Marriages, 1868-1925, index and images, Family Search). They were in Watertown, Tuscola County, Michigan in 1880. By 1900 they had two daughters and were living in Vassar, Tuscola, Michigan. By 1910 they had moved to West Bloomfield, Oakland County, Michigan. They were in that same place in 1920. Emma died in 1926 (Michigan, Death Certificates, 1921-1952, Family Search). John was still there in 1930 with the two children of his dead daughter, Ella Bowman Lemon, and his unmarried daughter, Hessie J Bowman. In 1940 Hessie is living alone with one nephew, John Clayton Lemon, Jr., who is listed as "John Booman," an obvious misspelling of Bowman, and he's using his grandfather's surname. Hessie died unmarried in 1945 (Michigan, Death Certificates, 1921-1952).

I am almost certain John Bowman died in Michigan between 1930-1940. I have tried everything I know to find him. His wife and unmarried daughter are not listed on Find A Grave. Plenty of John Bowmans on FAG, but none in the right place at the right time.

Oh, how I wish I had access to the images of the death certificates between 1921 and 1952! I know it's probably a case of misspelling of his surname.

In every census record, John lists Illinois as his place of birth. I cannot find him in Illinois unless I know his parent's names.

Why is he hiding? Why is he forgotten after his death? Where in Illinois was he born? Who were his parents? How did he come to be in Fremont, Tuscola, Michigan in 1879?

This is driving me crazy.