I remember having seen this in a picture. Can't find it tough. It was a huge wing mounted vertically. About one meter high.
First: Boy that was ugly.
Second: I can only imagine that this thing would be hell to controll in an autorotation, since that wing would fly backwards with a lot of undesirable aerodynamic effects. The forces on that wing could be higher than what the pilot is capable of holding, because the center of lift would be way out of the normal range. Even if the pilot would be able to control zero lift, the "wing" would be dynamically instable and one would have to fight every single moment to keep the helicopter from spinning.
Third: In forward flight, there would be very little to no effect at all and therefore almost no yaw control, hence the ship would need another thing out there to keep it fly straight. How about a tiny tail rotor?
Forth: If one tried some fancy maneuvers like flying sideways a bit too fast, interesting things could happen.