Zhan Jingshu truly lives up to his name. Even when he "disappeared," he left behind some clues to help his Master and the others find his location once they realized he was missing.
Perhaps he predicted his own disappearance, which is why he left clues every time he acted.
It's uncertain whether it was the "kidnapping" before his journey into cultivation that made him cautious, or if the later experiences in the cultivation world made him mature, leading him to prepare so extensively.
Initially, Murong didn't remember this, but upon returning to the Hidden Immortal Sect, the Master's first reaction was to take him to Zhan Jingshu's room to investigate.
