Based on Darne's southern service during 1861, I would recommend you contact your local chapter of the Sons of Confederate Veterans. If you don't have one close to you, Google a local chapter in the St. Louis area, and contact them. The SCV do work in Jefferson Barracks National Cemetery, and may know how to work through this delicate issue for you. One of the main activities of the SCV is the proper marking of Confederate graves. Darne was not in regular Confederate service, since active Missouri troops were not converted until early 1862, but I think his southern service should qualify him for their help.

Bruce Nichols