Mystery ghost page not appearing in Admin

For anyone interested, it was the SEOyoast plugin that caused the problem.

I turned it off and on, than the page appeared again in the admin.

After that I rest the settings for the page and it now works as expected and accepts its template.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)