Hi adamfilip,
It seems that you are mixing the shadow catcher technique with the Render Layer technique.
The Matte option is the old method, and since it used with a diffuse material, you cannot have the reflections on the floor.
My suggestion is to remove the matte option and work only with the Render Layer option by assigning a different id to the sphate and the ground plane, in this way you can have both shadow and reflection layer:
Render Layer Passesciao beppe