Hi! You know I just have found out where he is buried. I can't verify it because I don't live there, but a lady I have been corresponding with has recently sent me some information on Allen family descendants. You are descended from the Follet wife but I'm related to her in a round about way as well. In the 1885 Iowa State census they are all there together. Obadiah Chase Miller married Lucelia Estella Follett who is the sister of Eliza A. Follett. Robert and Eliza are next door. Emery S. Allen and his family with his daughter Arminda Chloe is next door to the Millers.
Buchanan County Iowa was a real stronghold of Allens. Since he was married to Arminda after Eliza he may have been buried next to her. Betty Allen Davidson says that he is buried on 18 Dec 1832 in Littleton, Buchanan, Iowa. There are two parts to one of these cemeteries and I don't see it all on-line.
Do you have a marriage date and place for Robert & Eliza? I would like that. Thanks.