Brief description of the issue:
After some time, even one launch sometimes, it's not possible to find Spotify.app in spotlight anymore.
The Fix is to manually go to Spotlight Privacy options, add Spotify.app and remove it, to force the reindex of that folder.
Spotify is the only app exhibit this behaviour so I think it is a bug in the client.
Your device and operating system (e.g. MacBook Air, 10.10 OSX)
Type of Spotify account you have (Free/ Premium):
The app version of Spotify you’re using:
Any screenshots, if they can help to explain your issue:
Added a Bug, fix and after fix screenshots