... was there any missing persons investigation done then?
As with Search and Rescue, the concept of "Missing Persons Bureau" that we have today is dramatically different from that of the colonial governments.
The
Western Pacific High Commission (WPHC) was the Walmart of civil services: police, military, diplomatic, education, health care, judicial, etc. If something needed doing, the WPHC did it.
There was no such things as a "missing persons investigation" in 1940-1941. All the WPHC had to do was ask itself, "Have we heard anything about any missing persons?" The inquiry was not in writing. No forms were filled out. All the officers had to do was investigate the inside of their own heads to get the answer, if they had been in the office long enough.
OK, this is stated categorically, but it is just my opinion after reading a few thousand pages of WPHC material. I don't have a source that says this and I could be wrong. When Roger and I were in Fiji, I kept asking people, "Who was the coroner? Where are the records of the inquest? What did the law require?" The answer was, as far as I could tell, "The WPHC was the coroner; the bones file is the record of the inquest; there were no rules and regulations about how this was to be done."