Someone intentionally did it.

"Then? Are you here to persuade me to come back to London so nothing like this will ever happen to me again?" Kyra asked. 

"To be frank, I gave a serious thought about it, sis. But you stayed in this place for two days without even getting upset. You in fact enjoyed your stay here and gathered courage to reunite with your old friends and even went to the places which hold bad memories. This is a huge progress." Anthony said. 

"How do you know all this?" Kyra demanded. 

"Oh, don't scold me for this! I was worried about you so I asked my men here to send someone to look after you." Anthony said. He knows what happened yesterday. He knows that Justin was following her all day but didn't take any action as Justin didn't make any move. 

And, his subordinate was the person who made the sound that made Kyra and Oliver aware of Justin's stalking.