Hello. It is very possible that he was so worn out from the war, that he died prior to the 1870 census. I truly believe that happened to quite a few of the men.
I know there were two cases of that in my own family.
Or it is possible that he went on to Arkansas because when the war ended, it was as if a flood gate was opened and many people from the old South poured into Arkansas and other points west.
I have a lady in the town I am in, who was a Hamm but I believe she told me that her set was of German descent. Her uncle won medals in the 1936 Olympics.
Have you ever thought of checking the nearest Familiy Library of the LDS(Mormon) church? I actually had the opportunity to visit in Salt Lake City in 2006 and it was a wonderful experience. I just loved going down the aisles and checking all the books for the states I was interested in. I learned things that there was no way I would have ever found if I had not had the opportunity to visit there.
I actually stumbled on them or perhaps someone was guiding me that way, but I surely was proud I went.