In this case they probably brought in a fresh pack of cards, perhaps even bought from the Casino store with the stickers on them and still in the cellophane wrapper. Even on close inspection no tampering would be revealed because there was no tampering.
Yes, the cards were marked, but by design, not by something the dealer would have been looking for. It's a bit of a grey area, and everyone loves to see the Casino get reamed. If it weren't a casino but the local church trying to earn a buck for charity, public opinion would not be on the player's side. But it is a casino, a money greedy institution that will do everything to get your money into their pocket, so there we are.
One wonders to what extend they'll go out of their way to reimburse players who were a victim (by losing money to cheating players) of such "faulty material."