Are you talking about in the app drawer, the app called "Navigation"? Its there for me. Or are you talking about holding down the search button for more than a second and saying "navigate to......". That also works for me. The navigation app can't be deleted so if its not there, there is something wrong. You can also hold down the search button for more than a second to get the voice prompt and say "map of........" If you have bubble buttons turned on in maps (it's under labs in settings), you can then just press on the navigation button from there.