Some Pages Not Appearing in Admin Pages List..

..but these are still accessible via direct link, and are visible within the wp_posts database table. This has happened more than once, and to my knowledge there’s nothing different about these pages. It happens right when I publish the page and then go to check its order in the pages list. This is a big problem because I cannot edit these pages using the standard WP interface. Any assistance is greatly appreciated.

(I am not running any page ordering plugins)