Wouldn't the alternative be that someone drilled through the tile without otherwise damaging the tile? There should be noticeable cracks in the tiles at the very least if a hole was drilled. If someone was going to go through the trouble of drilling a peephole and using a telescopic camera to peep (which is really the only way to see anything given the direction and placement of the hole), wouldn't it be much easier to go through the ceiling and put a small camera where it is less likely to be noticed? I would hope that the average guest would see a camera poking out of a hole in the toilet and not shrug it off. In this case, there would be 3 possible scenarios:
1. A camera was used, but not a single guest ever noticed it.
2. A camera was used and at least 1 guest noticed but chose not to report it to the police.
3. A camera was used, a guest noticed it and reported it to the police, and nobody in the media ever picked up on the story.
To me, none of those scenarios seem more likely than the hole being the result of lazy work and not being a peephole.