I am working on identifying those buried in Oakwood and sent your query to the fellow who's heading up the project. See below.
I searched the Richmond Daily Dispatch for both Harmon and Hartmon, no joy.
Officers were usually buried at the Hollywood Cemetery.
You should visit the Richmond National Battlefield Park Chimborazo Visitor Center. I believe the Historian there is a prolific author by the name of Robert Krick. Chimborazo was the site of a very large Hospital compound.
I've asked our project leader to contact you.
The names below [Harmon] or any variable of the spelling is not on the list at Oakwood but it's still possible he is there. We are still putting together an accurate list of over 10000 names and may find him later but keep in mind we will probably never know the identity of several thousand men who are buried there. One clue may be that although Oakwood has a number of officers, from what I understand, most officers were buried at Hollywood, now the good news is that very soon a new book is coming out with the most up to date and accurate list of burials at Hollywood and I would say this may be worth looking into, if I can get more info on this book I will pass it on.