Are they invisible people? If Security had to check 4,000+ rooms in each hotel building every day, they would be busy from sunup to sundown, throughout the hallways. The chance of seeing them would be very high, but they were nowhere to be found and we didn't even leave the hotel for a whole day, visiting people on multiple floors. Some hotels have over 5,000 rooms in one building. There are 154,000 hotel rooms in Vegas. You can do more research on the matter if you wish, but from my experience, and from the numbers I've found, I seriously doubt anyone claiming every hotel room in Vegas is checked once a day.