Concerning Champion Hill, I remember stumbling on a source that claimed the expired wounded were simply buried in the yards of the houses serving as hospitals. I believe the way it was phrased was that not an inch of the yard was left that wasn't occupied by a freshly upturned mound of earth.

Two months later, Confederates buried in mass trenches were laying exposed where the rain had washed the soil away from the bodies. Given that nobody had taken the effort to care for the exposed bodies in mass graves, I seriously doubt anyone took the effort to disinter the individually buried bodies and move them to a graveyard.