You added the part about exfiltration from the country. It is possible he has been kidnapped by Chinese secret police in the country and remains in the country (at least until they manage to coerce him to return "willingly".) Anyway, nobody said anything about witness protection either, that part was your hallucination too.
By the way, before you get yourself all worked up, I think the much more likely possibility is that he has disappeared for a mundane reason, such as murder, or else he has deliberately disappeared himself for some reason.
