Although No3 sounds the most probable out of that bunch,I don't think it's any of the things you mention IMHO.
Sooooo if it did not crash or it did not land somewhere, what do you think happened? Aliens maybe....
Although this video is a fighter and concrete, you should get the idea.
http://m.youtube.com/watch?v=RZjhxuhTmGk
Anyone thought that just maybe the search and rescue teams are being incompetent.




