Trader Sarien:
I bet that the grave of the Orc Warrior that you are looking for was already excavated and destroyed. But they say that once in a while, the ancient relics are found in the ant tunnel so if you are lucky enough you might find the bones that you are looking for.
If my guesses aren't wrong, it must be the soldier ants who carry such things as bones and remains. I think they'll have cut it into 5 pieces more or less. Good luck, then!