In the movie, Sicario - Day of the Soldado, the American operators set up a surveillance team above the high school campus where they would kidnap a cartel's boss's daughter.
but we can see form this screen shot, there are plenty of tall building around their position and any one curious enough to spy around with a binocular would have seen them, I am assuming it will take the Americans days to stay there before they are confident enough to act.
The only reason I can think of is their window is one-sided visible, e.g. you cannot see through from the outside.
Any other thoughts?