Remains of casualties - including non-battle deaths - were interred in neatly arranged temporary cemeteries throughout the Pacific Theater of Operations, usually as soon as practicable after death. Beginning in 1946, the War and Navy Departments began contacting next of kin of all casualties buried overseas to determine their wishes concerning the final dispositions of remains. All remains of those whom next of kin requested to be returned were exhumed and returned to the U. S. between 1947 and 1949.
Some of the temporary cemeteries became permanent, the one on Iwo Jima, for example. Permanent sites were established after the war and remains from temporary sites were exhumed and reinterred in the new, permanent locations.
If it's within convenient distance, you may want to examine the headstone to determine whether it's an actual gravestone or a memorial marker. In some cases where remains were unrecovered or buried at sea, a memorial marker was placed at the request of the next of kin. Memorial markers are identical to gravestones except that the top line of the inscription on a memorial reads "In Memory of."