Do you absolutely need it? If you have another one handy, leave it in there and put the new stopper on with the airlock. If you don't have another one, you could use a sanitized metal coat hanger or a santizied big spoon. You won't get any off flavors from the stopper in there- in fact I think all of us have done that one or twice.
Oh wait- are you the young guy making horrible sounding beverages with bread yeast? If you are, believe me, you won't get any bad flavor from the stopper. The ingredients will do that for you.........
I imagine if you could get a coat hanger in there to snag the stopper you might be ableto pull it out, but boy would that be a trick! I'm new to brewing, but I would suppose that it wouldn't hurt anything being in there as long as it was sanitized. You may just want to get a new stopper.
Or as a last resort, take a hammer....umm...never mind.