Unknown Facebook page owner – Web Applications Stack Exchange

Recently we found that we have a page owner named Backup3 in which he is unkown for us. when we searched using his ID no.

This was what appeared:

This content isn’t available at the moment
When this happens, it’s usually because the owner only shared it with a small group of people or changed who can see it, or it’s been deleted.

How can I regain theownership of my page, we are still admins on the page yet we need the owner to allow us access some of our settings.

thank you