I'm the last one who believes in conspiracy theories, but in this case..............
Clearly I've got no idea what happened, but I do believe that "someone" knows where it is.
U.S.A, China, Russia, take your pick, but I refuse to believe that one (or more) of these players aren't watching the world 24/7.
Possibly it doesn't suit them to 'advertise' their methods or capabilities or even the fact that they watch that area.
One day, someone will tap someone on the shoulder and say "Why don't you got and have a look in this certain area" and a week later we'll hear "It's a miracle, against all odds the wreckage has been located!".
TTS