No one can actually disappear. When a monk in Soul Of The Beast disappears, he is blocking people from seeing him through mind control. Could mind control be used in the real world to make someone seem to disappear? To my knowledge, this has not been confirmed, but it should be possible.
To a minor degree, mind control is already part of our everyday lives. It is so common that we don’t see it for what it is and accept it as normal. Our minds are controlled with advertising, propaganda, movies, television, radio, stirring speeches, bad news, good news, what we’re taught in school, and even gossip from a neighbor.