Could this be survivorship bias? Those are the cases we know about, but what are the odds that the cases we've seen just happened to be the only cases happening

Could this be survivorship bias? Those are the cases we know about, but what are the odds that the cases we've seen just happened to be the only cases happening? Some random student being disappeared from campus hitting the news indicates to me that MANY people are being disappeared. I don't know what the rate of disappeared vs left paper trail is but I can't imagine it's a good yard stick for "close enough to be useful for approximating a count of all of the cases"