Thank you Steve I appreciate your answer. It is basically what I suspected would be the case but sorta hoped angainst logic perhaps there was some sort of documentation on how the original burials were conducted. I guess all the men unaccounted for are now truly Unknowns. There are gravemarkers for a few of them in hometown small cemeteries but I suspect they are all just empty graves, a place for families to leave flowers. There is no good way to know if any body had been actaully retrieved somehow and brought home for burial. Logic says no one was retrieved.
I can tell you that it was chaos for the Union regimental company clerks also. They had no real way of knowing who was missing, who was dead, or who had been wounded and carried off the field for treatment in several locations... all were scattered on the wind. The clerks based their reports on rumor mostly it seems like and only long afterwards did they get a better sense of who was where. The rosters are full of errors. Promotions were even made to take the places of "dead" lieutenants who later turned up alive in Camp Ford at Tyler Texas and the new promotions had to be rescinded.
Anyway I thank you for your answer and Art and Jamie too.