Your post was very helpful in sorting out the Mary Herron-Goddard-Trobee-Heinmiller connections. Based on your information, I think I've found Frank Brown Trobee in the US census files for 1900 and 1910. There's a Frank B Doan listed as the adopted son of Silas and Dora Doan in Triumph Township, Custer Co, Nebraska. In 1900, Frank B Doan's parents place of birth are both listed as "unknown" and in 1910 as "United States". In the 1920 census, there's a listing for Frank Trobee in Burt, Logan Co, Nebraska, married to Mahalia, with three children (Francis, Dora and Robert). The names and ages seem to line up with other records for Frank Brown Trobee. Does that seem like a fit with your family's information?
Maggie