Definition of "missing"

Forty three killed and 80 wounded in action with the Implacable. 180 killed and miſſing in action with the Centaur.

1808 October 1, “State of Public Affairs in September. Containing Official Papers and Authentic Documents. [Killed and Wounded on Board the Emperor of Russia’s Late Ship of War Sevolod.]”, in The Monthly Magazine, or British Register, volume XXVI, part II, number 3 (number 176 overall), London: Printed for Richard Phillips, […]; printed by J. Adlard, […], page 281, column 1

She was so mad she wouldn't speak to me for quite a spell, but at last I coaxed her into going up to Miss Emmeline's room and fetching down a tintype of the missing Deacon man.

1913, Joseph C[rosby] Lincoln, chapter 6, in Mr. Pratt’s Patients

How likely is it that all the people who are described as missing are living together in a small town somewhere?

1997, George Carlin, Brain Droppings‎, New York: Hyperion Books, page 71

The treatment of missings is a problem in statistical software.

1997, S. Klinke, Data Structures for Computational Statistics, page 27

Patterns of missings across the whole data set are readily visible, but also patterns which only apply to small subgroups of cases.

2002, David J. Hand, Niall M. Adams, Richard J. Bolton, Pattern Detection and Discovery