It was a night flight. Many pax will bee asleep or dozing. A gentle turn will probably go unnoticed. So even if there was some malicious event occurring, e.g. an act of piracy, the passengers may have not even noticed that anything was wrong and switch on their phones to contact people (as 9/11 told us they would).
I don't know where all this "gentle turn" business is coming from. Officially, we don't have any confirmation that the aircraft deviated from its track.
All the unofficial leaks so far have indicated a "sharp turn towards west".
And *if* as the latest NYT leak indicates, your behind was launched 10000 ft up into space, and then dumped 20000 ft I think you'd notice, sleeping or not.