Yes #3 tells a lot. Video games are actually boring...unless you are playing it. She should not have been distracted to notice the N900.
Uhm... If we're talking in terms of "should've", should we not mention personal responsibility first as well?
Assuming OP speaks the truth and is not just playing another stupid/boring game, I find it quite silly to position your device in such a way that this "accident" could actually take place.