Simple answer? The war moved on.
The Marines were buried in, IIRC, four hasty cemeteries. They were buried in trenches, head to foot and wrapped in their ponchos.
The graves and who were in them was recorded - and the records are still available.
But the area was paved over (one of the grave sites), runway built - and the war moved on.
Friend of mine has an uncle in the grave noted in the story and his remains were next to a positively IDed body. Just waiting on DNA tests to confirm.
Makes sense: I would suppose it was mess mainly because (at that stage of the war) the importance of graves registration hadn't yet been learned.