My videos on my iPhone and iPad don’t reside on a server, unless I do a backup of my entire device. I can also turn that off, as a function. SO ... in light of that, I don’t know why you would expect it to be on a server.
Anyone who viewed the video on a device other than the original probably put it on a server-synched device. A PC for example, as a file. Backed up automatically. Shared with a few close friends in the lab. Sent to a personal email account. Etc.
It’s like Lois Lerner’s emails or Hillary’s server. The data is out there. It is highly unlikely that they have hermetically sealed off all possibilities of digital copies.