Your ancestor's story is also of interest to me. My g-g-grandfather, Albert Slattery, marched with the 8th Minnesota till he died aboard a hospital ship (probably just the riverboat that supplied the regiment) on August 25, 1864. I have reviewed several soldier accounts at the MN Historical Society. None mention him. His service and death were unknown to my mother (his g-granddaughter) and her siblings until I discovered it. This "hidden" story is fascinating to me as Albert Slattery's daughter, my g-grandmother, was born in October of 1864, and so she never knew her father. Another distant cousin filled in the family tradition which included a story that he fell from a cliff. I did find an account from a Wisconsin soldier who was also on Sully's expedition stating that the riverboatmen did not take good care of the ill soldiers. Albert Slattery served in Company H. It is not clear what they did with his body?