GES convention services hired a bunch of us through the electrical Union in LA. That's all the proof I can really give you. We aren't allowed to have phones on the expo area during setup.
What would be hard to believe? A replica of a ghorn (the most recognizable and desired weapon in the game) is almost the only thing it possibly could be.
Think about it. Even if the next dlc has an even better weapon coming, people would just see it and be confused because they don't recognize it. People will immediately go crazy to see or snap a picture of a "real" ghorn.