Liam was not looking good after what he had discovered in that warehouse. He searched for Zhen-Zhen and others but he didn't see anyone.
In the end, he just went home to gather his thoughts. He was quite shaken after confirming his suspicion.
Now he understood who was the person releasing those magical forces around the school vicinity.
The first time he met Zhen-Zhen he already sensed something strange about her. He thought he was just mistaken but it turned out that Zhen-Zhen was not an ordinary person.
Liam reminisced those moments when he sensed Zhen-Zhen's magical force. He knew that it was a magical fire that burned Jade's and her friend's cell phones.
This also explained when Liam saw Tristan outside the gym near the storage room where Zhen-Zhen had built an invisible barrier during the Acquaintance party. It was indeed Zhen-Zhen who created the barrier.