5 C.F.R. § 880.101
(b) This part establishes the procedures that OPM will follow to—
(1) Determine—
(c) This part applies only to situations in which an individual who satisfies the statutory definition of an annuitant under section 8331(9) or section 8401(2) of title 5, United States Code, disappears and has not been determined to be dead by an authorized institution. This part does not apply to—
(2) A separated employee who either—