You can force Spotlight to re-index the drive by going into the System Preferences and choosing Spotlight. When it appears, click on the Privacy tab, then drag the hard-drive icon into the window. Doing so tells Spotlight to ignore everything on the drive, so it makes Spotlight's search database useless, which is what you want if the database is missing stuff.
Then click on the drive icon you just moved into the window, then on the minus sign at the bottom. This will remove the newly created privacy setting, and force Spotlight to completely rebuild the search database.