Yes but no plane would hit the water without breaking up, surely?
So there has to be debris in the area, if that's what happened. The flight recorder locator beacon automatically activates on immersion in water and lasts about 30 days.
As for the theory that if the plane landed and no claims or demands have been made so far, it takes time to hide 200plus "hostages" which could explain the delay.
Either way this is a very bizarre incident and I feel for the families of those on board.