One of my drop down menus, the "Create Content" option under the parent "Content" tab has dissapeared. How can I recover it? (I'm using Drupal 7)
It looks like you're using admin menu, right? A blog post about rebuilding the drupal admin menu says you can:


Delete you current links via SQL DELETE FROM menu_links WHERE menu_name='management'.
Clear all caches at Administration > Configuration > Development (or just: http://example.com/admin/config/development/performance if your menu is ruined at this point). Drush users can of curse use drush cc all or even drush cc menu


Disclaimer, I didn't try it myself. Hope this helps.