Inertia everywhere

Your answer is correct!
The ball stays where it is.

Because of its inertia the ball retains its state of movement: It is in rest and would like to stay in this position. Therefore the ball (almost*) stays where it is.

Surely you know similar experiments, which are based on the same principle. For instance, the trick to pull the tablecloth away but the dishes stay on the table without damage anyway.

*Because of friction effects the force, which is needed to move the cardboard, is partially transferred to the ball. This is why it moves a little bit in the direction of the cardboard.