My grandfather was stationed at Pearl Harbor in 1940 in the 64th Coastal Artillery Regiment, Battery C. In the months following the surprise attack at Pearl Harbor the War Department decided to take the fit, fighting soldiers from Coastal units and attach them to Marine units and sent them to fight. We know that he saw action in Guadalcanal and Bougainville and may have spent some R&R in Fiji at some point before returning home in '44. Is there any way to know what unit he was reassigned to or establish a timeline of his movements without those crucial documents that were lost? I imagine not, but worth a shot. His experience, like many, was not one that he liked to talk about so we only have small bits of information to go on.
Hello there! As your question is related to looking for identification/information regarding military personnel, our Guide on Military Identification may be of use to you. It provides a number of different resources, including how to request service records from a number of national agencies around the world, as well as graphical aids to assist in deciphering rank, unit, and other forms of badges or insignia. While the users here may still be able to lend you more assistance, hopefully this will provide a good place to start!
Also, please remove the name from your post above and let us know when you've done so. Thanks!