My guess is a miscommunication....probably between Stern and the distributor.

Stern does ship directly from their factory to customers. Stern do provide demo units for shows that sometimes go back to their factory (though I am a bit surprised they do that with LE models). So this could have been a case of the distributor calling Stern and asking if they had any Deadpool LEs left, Stern saying yes and then the sale going through and Stern getting the paperwork to ship out the game to you. Stern may have even mentioned it was a demo unit to the distributor and they didn't catch that....or maybe they thought you would not care or notice. Maybe the demo unit was just logged back into inventory by mistake. There are probably a lot of small mistakes or miscommunications that could have happened to cause this issue for no nefarious reason.

So someone might have been trying a sneaky on you, but it could have just as easily been a miscommunication. In either case, it sounds like you are on top of things and I'm expecting it will get resolved.

Now I want a pinball machine done entirely with your dank photoshop skills. I thought the watermarks were my favorite part until I saw that poor busted pinball leg.