Completely M.I.A. - Tradução em português

I've watched the serie "Supernatural" then I came across with this speech of Dean:
"They found his car, but he'd vanished. Completely M.I.A."
However, I don't understand which meaning of "M.I.A.". Then I searched the subtitle in Portuguese and there was written:
"Totalmente desaparecido."
Can someone say me why "M.I.A." means "desaparecido"?