1999 Plymouth Voyager Key will not turn in the switch

I tried to start my van this morning, and the key would not turn in the ignition switch, I also noticed the steering wheel was not locked, and there was a 5 centameter round peace of white nilon rod tapered on one end and honed down on the other laying on the floor. If this is the problem is there a diagram to show were it belongs and the procedure to replace it