It comes doweitit probably came down to time and money and where not able to shoot a more fitting angle, or forgot to and time ran out, or, the editor effed up. But seeing as how it doesn't impact the rest of the movie it's a "meh" moment

I have to assume in reality she saw the toy and saw the open door to the car and just had to figure he was in it. Long shot being that she may have caught a reflection of him off the windshield and even longer shot off the rear view mirror.