Why can't Spotlight find an application I know is there?
It is quite possible that your Spotlight index is damaged or incomplete. The app does launch and function correctly, right? If so try rebuilding the Spotlight index.

Launch System Preferences, Click on Spotlight and then click the Privacy tab. Drag your HD icon into this window. Click OK when asked to confirm.

Other housekeeping utilities (like Onyx) will also rebuild the Spotlight index.