No. And neither did Dr. Phil and he obviously understands a little something about child development. Are you a doctor?
You do not know either the city or her child - the mother does. Nine is old enough for some children to make their way on public transport - even in a big city - if they have been taught how be safe. And he knew the subway system because his mother had spent time taking him on trips and making him comfortable and familiar with it.
When I was 9 I was walking a mile to school alone and walking back alone. When I was 8 I was riding my bike or walking to the local 7-11 or Thrifty to get candy or ice cream in the summer. We played outdoors in the empty fields and creeks, built tree forts and (gasp!) cross streets alone. We did our own laundry at that age, and knew how to cook simple things. But our mother had spent years covering these bases before letting us do it ourselves - walking these routes with her so we knew how to cross streets, how to use the stove safely, etc. We learned to handle ourselves bit by bit. I'm sure she worried - she's a major worrier. But she let us stretch our wings. I suppose now that you will decide that my mother was a child abuser, too.