Truthfully if he had been left at De Valls Bluff, the remains would probably still be there and his grave marked.
There would have also been someone taking care of the grave would be my opinion.
But it is my understanding that the contracted folks were not careful how they handled things, so it is pretty sure he was moved and now no one knows anything.
I would suggest you research this further and looks for more clues in the existing records.
Good luck.