Another resource at the OHS Archives that may assist you is their newspaper collection. Through several newspapers from the general area, looking at days before and after you may be able to find a death notice or an obituary that may provide the cemetery name. With the name; or with a general town area you can go to some of the funeral homes in the area. I have heard that some maintain cemetery records, or can redirect you to the location of these records that may provide a plot number and location within the cemetery. Good luck in your search for your ancestor.