It is hard to diagnose the cause of the Polyscias leaf drop without knowing how much light it received inside and what your watering routine was.
For now, do not let the soil get very dry. In the photo, it appears that the outer roots of the rootball are exposed to the air and they should not be. Also, get it back inside or keep it in deep shade outdoors, assuming your outdoor temps are above 60 degrees F.
Ming Aralias like to be kept moderately potbound with the soil moderately damp at all times. They do best indoors in a moderately sunny window, such as close to a north or east facing window. They are quick to shed leaves if the light is changed and/or the watering is not maintained.
