“Absentee” means either of the following:
(a) A member of a uniformed service covered by United States Code, Title 37, Chapter 10, who is determined thereunder by the secretary concerned, or by the authorized delegate thereof, to be in missing status as missing status is defined therein.
(b) An employee of the United States government or an agency thereof covered by United States Code, Title 5, Chapter 55, Subchapter VII, who is determined thereunder by the head of the department or agency concerned, or by the authorized delegate thereof, to be in missing status as missing status is defined therein.