Air France was sending ACARS reports. They new the general area and while they found debris they didn't find the airplane for 2 years. The thing is if it blew up where? Common practice is for the Captain to declare a emergency as soon as possible. This crew didn't do that. If it was a hijacking the crew is supposed to send out a signal to atc. That supposedly didn't happen either. Only a few scenerios can be made from this.
1. Instantly blown up. But if that is the case debris should have already been found. unless the plane was off course.
2. Turned back and crashed possible but crew would have declared emergency first.
3. Hijacked by Passengers. Crew would have sent distress message before breech of cockpit.
4. Hijacking by crew. Too me the only situation that makes sense at this moment. Either the Captain or first office disable the transponder and hijacked the plane and crashed it.
There is more going on than what is being let on. It will come out in time once they get more details. imo
You are leaving out loss of communications. Highly unlikely given the redundancy in systems, but not impossible.
Regarding finding the debris, its an awfully big ocean out there, and debris is not always that easy to spot. We can hide an aircraft carrier from spying eyes, so finding debris can be difficult if you don't have a relatively localized area to look.