Wasn't there another case similar to this. With another plain about 15 -20 yrs. ago? I think the only difference is they new where the plain crashed. They just were unable to retrieve the bodies and plain.
I could only find one flight that could be similar to mh370. Air France Flight 447 crashed into the Atlantic Ocean and killed all souls on board. They knew where this plane crashed but still took 2 years to find most of the plane and black box, even longer to figure out what actually happened. source
I believe there was another plane that crashed into a mountain range and it took a very long time to find also, I saw it in one of the articles about mh370. I just don't remember enough details about it to find more information about that crash. :/