How can I restore Spotlight to menu bar?
Just to make an official answer.

User M K referenced an article in osXDaily that explains how to both hide and un-hide the Spotlight icon.


  Show the Spotlight Menu Again
  
  Getting the Spotlight icon back is a matter of bringing the permissions back to their default setting in OS
  X. Go back to the Terminal app by relaunching it from
  /Applications/Utilities/, and then enter the exact command syntax
  below: sudo chmod 755
  /System/Library/CoreServices/Search.bundle/Contents/MacOS/Search
  
  Hit the return key, then follow this up with killing the
  SystemUIServer process again: killall SystemUIServer The system menu
  bar will refresh, and the Spotlight menu will be visible again.


I just tested this on OS X Yosemite 10.10.5 with success.