In any other gun, I'd suggest a broken shell extractor to remove it....but they don't make those for 12ga's.
I'm going to go and grab one and stick it in the chamber and see if I can get it back out. Might help you.
I can really believe that came from the dealer like that, too. I've seen worse. I had one fellow on the phone for close to an hour once trying to explain to him that a Speedfeed stock just held the shells at the ready, not load them into the shotgun as it was being fired. He was convinced those four extra shells would somehow load from the stock to the receiver by themselves....a dealer had told him so.
Sh*t happens. It happens to all of us.
Ok, in a used/slightly dirty barrel chamber that little sucker is a tight fit. I couldn't get it in as far as yours without some considerable force and that, I didn't want to do. In a new barrel, though, it's a snug fit but it goes in as deep as yours in the pic and I can work it out with my finger. Don't use a multitool yet! If it bends the edge of that choke tube the slightest, the tube will be ruined. That's $8. Try sticking your index finger in to the far edge of the tube and flex your finger so it's tight in the tube and try to work it out. I have big hands and mine worked pretty easily. When we had you closing the bolt, it shouldn't have pushed it in any harder, though, so that should be ok.
Barring the finger, the best I'd suggest would be a clothes hanger wire tool bent into the proper shape with two hooks on the ends of the wire. Try the finger.
rich