Page can not be updated and disappeared in “show all page”

You can try to repair your database. To do it, please read this answer in StackOverflow.

If repairing database didn’t worked, you can try to update the post status manually.

  1. Connect to your database
  2. Find the page in the wp_posts table (you can find it through the post_title field)
  3. Update the record running a script like this one:

    UPDATE wp_posts SET post_status=”publish” WHERE ID = YOUR_PAGE_ID