behind the curtain, behind the scenes, camouflaged, concealed, disguised, hidden, imperceptible, indiscernible, insensible, invisible, latent, out of sight, secret, sightless, submerged, unapparent, unbeheld, unbeholdable, unconsidered, undescried, undetected, undiscernible, undisclosed, undiscovered, undivulged, unexplained, unexplored, unexposed, unheeded, unmarked, unminded, unmissed, unnoted, unnoticed, unobserved, unperceivable, unperceived, unrealized, unregarded, unremarked, unrevealed, unseeable, unsolved, unspied, unthought-of, untraced, untracked, unviewed, unwitnessed, viewless