He Later Went to the South

There is a file in the filing cabinet of the subdistrict office, and a person appears three times: One move-in, one move-out, and one death cancellation. But this person cannot be found in the original book. The neighborhood committee said: The name sounds familiar, but I can't remember who it is. The neighbor said: The person who lived on the third floor used to be a nice person, but then he disappeared. Archivist Zhou Yuan wrote down the incident. He spent a year looking through pay slips, looking for old photos, and asking everyone who might remember. Finally he put a note on the portfolio: "Chen Jianguo, he later went to the south." Then he put the files back in the cabinet and closed the door. The book does not trace where he went. I only want to ask one thing: How did a living person disappear from everyone's memory.