Ahhhhhh!
I work at Toys R Us, as many know. I have zero loyalty to the company; what I'm about to say isn't motivated by love of my corporate mother. I'm just a low level guy earning money while in college.
But seriously, there is exactly one type of customer I hate, and it's the ones who think that its our fault when games don't arrive on time or we don't have enough of them or something. The girl was absolutely correct to assume the game would be there when it is supposed to arrive. She is absolutely correct that the game is likely to sell out. The only problem here was DHL, and Toys R Us has no control over that. It isn't their fault: you're just blaming them because they happen to be the people standing in front of you when you found out.
I would have done precisely the same thing as that girl/manager, by the way. There's absolutely no way to know that a shipment is going to be delayed by DHL. Should we have told you to come at 2, when the new shipment arrives? I can tell you this: if that had been my store, you wouldn't have gotten a copy, as we were already sold out at 1 PM. That would have made you even more pissed, I can assure you of that. They can't win.
And most people don't get upset, they just say "no problem" and move on, and come back later.