Given that no-one has yet indicated where the VS was found, isn't it a bit early to be deciding whether it was cause or effect? If the VS came off at altitude and "floats like a leaf" through the air then it would in all likelihood have been some distance from the main debris field and the Brazillians (who appear to be doing an excellent job) would have had one heck of a job to find it. If (as seems likely) it WAS with the main field then it may have still been attached to the airframe even - depending on attitude - at beyond the point of impact.
It isn't possible to make an infinitely strong aircraft. If sufficient forces apply, something will break, but at this stage we really don't know whether the strong force was aerodynamic or hydrodynamic.