Indeed, it should be good practice for any journalist to download copies of online material they are reporting about (not just video, but anything), for the cas

Indeed, it should be good practice for any journalist to download copies of online material they are reporting about (not just video, but anything), for the case that they are being deleted or altered. In the old world, you had a piece of paper or a document that you could store somewhere. An URL is not a way of storing the content, it can always disappear.