The message Harold Finch (Michael Emerson) wrote down at the end of this episode: "Sierra Tango Oscar Papa". In other words, "Stop" using the "ICAO Phonetic Alphabet".
Scenes in Maple, NY were filmed in the towns of Tappan and Piermont, both located in Rockland County, New York.
Root refers to Shaw's situation as Schrödinger's cat. Schrödinger's cat is a paradoxical logic problem: when does a cat, locked in a box with a device that will eventually kill it, definitively become either dead or alive? Drawn from quantum mechanics, the study of quantities that can change only so much, and no more, it was initially applied to the physical state of matter. In more popular use, it has become an aphorism referring to situations analogous to a state of limbo. However, unlike limbo, Schrödinger's cat asks a critical question: when does the uncertainty end, and the cat become one or the other, dead or alive? To the team, Shaw is neither dead nor alive until they know which, leaving her, and them, in an unresolved state which each must reconcile for themselves. Only we, the audience, know which is true.
M.I.A. is the acronym for Missing In Action, a military term used to describe troops who cannot be found or have not returned to base after an engagement. In this case, Shaw can be termed M.I.A. because the team cannot determine her whereabouts, or whether she is dead or alive.