CKEditor disappeared
I recommend you to do the following and I hope it will fix your issue


Clear drupal cache then check CKeditor field 
If nothing changed then try to open your site on different browser 
If nothing changed then try to look if you have any javascript errors when you edit any content/node/settings; use firefox with firebug add-on
If nothing changed then try to uninstall the module then install it again 
Also try to disable javascript optimization under performance menu