this idea is assuming the stopper has no hole in it.
after your beer is racked out, put some very cold water in it. Turn the carboy upside down and try to get the stopper to plug the opening. Then warm the carboy with light heat. Do this as slowly as you can to avoid thermal shock to the glass which will make it shatter. Maybe start with warm water poured over it, then step up to hot tap water and then heated water. As the air in the carboy expands it should push the stopper into the neck. If your lucky it may get pushed all the way out. Otherwise, hopefully it will be wedged in there enough that you can grab it with pliers or stick it with a sharp hook or something to pull it on out. BTW if you want to try this method don't be tempted to lubricate the opening since you want the stopper to be wedged in the opening to avoid it slipping back in to the jug. oh, and good luck. If it works we all need to have a moment of silence for Mr. Wizard