William H. Hauenstein who was born 1822 was married to Maria E. Steigleman, who died in 1888. As you mention, on the 1900 census, he is a widower living with his daughter and her husband (John Fogleman). It's possible there was a very brief marriage - but it's not mentioned in any material written about the family (Miller County history book, newspaper clippings, Peggy Smith-Hake articles). That doesn't mean it didn't happen, but there's no evidence to support it either. If you find some, please share. It's an interesting mystery.