Sounds like you answered correctly.
There must be some upward force beyond the critical AoA, though, because of the relative wind hitting the underside of the wing. This cannot be described in quite the same way as pre-stall aerodynamics but you can see that there is still a force acting perpendicular to the underside of the wing, it's vector being very much aft and sufficiently so as to be mathematially infinite.
You will remember that up to a third of the lift created by the wing comes from the underside. This is the physical pushing up, the remaining two thirds being the difference between the pressures, top and bottom (bernoullie's principle).
What I'm trying to say is that when the C of P for the top half of the wing ceases, all that is left is the C of P on the underside which has a rearward component.
I'll have a lie down now!