On the matter of falling unconscious: Did the victim make a Spellcraft check to know what spell was being done to them, so that they had time to shift their stance? If not, in my opinion, then the only way they'd remain standing while prone is by shear random luck.
On the matter of held items: If the victim falls to the ground, the chances that they'd maintain an uncontrolled grip on any object is very low. When unconscious, muscles relax and digit muscles return to their un-stretched state. This is unlike other status affects that cause a bodily surge or charge of tension. In my opinion, it is unlikely that common object would be held in grip, unless any other fastening or adhesion was applied.