Every private room in Paradise Dynasty was equipped with CCTV because most of the decorations inside were antiques worth a lot of money. Hence, aside from a matter of privacy, art appreciation was also one of the reasons why people tried to reserve it.
It wasn't just a symbol of status but a place of inspiration and art criticism which evaluated one's knowledge. After all, this was one of the ways the upper crust flaunted their status.
Hence, Killian's first instinct was to check the camera inside the room. To keep a complete lookout for their antiques, surely they would install a 360 degree camera that covered the whole space, so it was highly possible that the balcony was within the range.
Unfortunately, Killian had to be disappointed. When he watched the footage, the balcony was completely blocked by the sliding door. It was as if Lila had planned this beforehand.