The Bellagio vault robbed by Danny Ocean and crew is presented to Terry via a faked video. Terry realizes the fake later on when he realizes that the vault floor in the tape does not have the word "Bellagio" on it. He says
"Does it say 'Bellagio' on the vault floor?"
We had it installed Tuesday. The images we saw of those men robbing us was a tape.
If the crew had been staking out the casino, wouldn't they have seen workmen coming in and out? Replacing a floor is not a simple thing. There doesn't seem to be any mention of their awareness that the vault floor was changed, though one might think that that would scuttle their plans as it would be an obvious tip-off to someone paying attention to the taped version -- and they expected Terry to watch.
Did they know the floor would betray them? Were they counting on that, or did they just get lucky that Terry didn't notice the difference sooner? Did they account for the presence of workmen when scoping out the date and the access to the vault?