Mobile phone plot flaw (spoiler)
Isn't it a bit too much of a coincidence that on the very day that she gets killed, Stevie just happens to lose her secret second phone -- which she has successfully managed to keep hidden and secret for months -- in River's car, and no one notices it amidst the rubbish on the floor.
It would have been far more believable if the phone had been in the lining of her coat, or some other hiding-place