I am the Great-Great Grandson of Fritz and Louisa. I am also trying to figure out what happened to Fritz. The 1870 census shows Louisa and Fritz and their family. In 1880 Louisa is widowed, according to the census, and she is living with her son Henry W. Hemme,"helping house." Henry W is my Great Grandfather. His son Alvin is my maternal Grandfather.
There is a Fritz Hemme that died in Leavenworth, KS in a veterans' hospital in 1906, and his record shows that the hospital notified "Louise Hemme" in Higginsville, MO, which means it is not our Louisa(dead). The form also lists Fritz's closest relative as Herman Hemme, brother. I have not been able to find reference to Herman, even by searching middle names. The Fritz in Leavenworth is probably not our Fritz.
Have you found any more info on Fritz since your inquiry in 2007?