miss·ing 
/ˈmɪsɪŋ/ adjective
/ˈmɪsɪŋ/ adjective 1 : unable to be found : not in a usual or expected place
▪ My keys are missing. [=I can't find my keys] ▪ One of his front teeth is missing. [=he does not have one of his front teeth; he is missing one of his front teeth] ▪ a missing tooth ▪ missing children — often + from ▪ A few books are missing from the shelf. ▪ She discovered that some important papers were missing from her desk. — sometimes used in the phrase go missing ▪ My keys have gone missing again. [=I cannot find my keys again; my keys are missing again] ◊This phrase is more common in British English than in U.S. English. 2 : needed or expected but not included
▪ The new director has provided the missing ingredient that was needed for the show's success. ▪ It's a good sauce, but there's something missing. [=it lacks something that would make it better] — often + from ▪ There was something missing from his life.
▪ My keys are missing. [=I can't find my keys] ▪ One of his front teeth is missing. [=he does not have one of his front teeth; he is missing one of his front teeth] ▪ a missing tooth ▪ missing children — often + from ▪ A few books are missing from the shelf. ▪ She discovered that some important papers were missing from her desk. — sometimes used in the phrase go missing ▪ My keys have gone missing again. [=I cannot find my keys again; my keys are missing again] ◊This phrase is more common in British English than in U.S. English.
▪ The new director has provided the missing ingredient that was needed for the show's success. ▪ It's a good sauce, but there's something missing. [=it lacks something that would make it better] — often + from ▪ There was something missing from his life.
missing in action
— used to say that a soldier cannot be found after a battle and might have been killed, captured, or wounded ▪ soldiers who are missing in action and presumed dead
