The bolt has a groove. If you move the backseat while pressing the unlock trigger force is applied to the bolt and the metal hanger which is connected around the groove could detach from the bolt. So the bolt is not moving anymore but locking the backseat.
You could try to move the bolt in direction of the groove to unlock your seat.
Marked the position of the bolt on one of the pictures from the thread creator.
Hope this helps. Did this repair back in 2015 and learned to first press unlock and then move the backseat.