There's nothing unbelievable about this. There's a lot of f'ing water out there. It took two years or so to locate that Air France flight at the bottom and they had debris to go on. These guys have little more than their dicks in their hands to base a search from, so it's not a shock the plane isn't in the initial location.
Now while this is no doubt "proof" it didn't go down in the ocean to the tinfoil hatters, it really only means one thing. It's a big f'ing body of water and it's really hard to find things at the bottom, especially without a solid starting point. The end.