In the very end, so what?
Even if someone would literally see him disappear and reappear what they could do? Report him to the police?
I dunno if they would go "death note" and having some genious L telling them that mysterious deaths all over the world are caused by a single japanese boy that magically kill people with his mind or some alien device, and everyone would agree with it cause "he is L, if he say so it must be so cause he is soooo smart".
Realistically the cops or any judge would laugh even at a literal video, thinking is some kind of filter or effect. And tell them to fuck off.