Where are you located?
The album is not available in these countries:
Like @sydneyhazelton said, the availability of music on Spotify is up to the artists and their music label.
If the music is gone, the artist or their music label has likely decided to remove it from Spotify.
Sometimes the music is only available in certain countries, while access is blocked to others.
Sometimes the album or song will be unavailable temporary, and come back again later. Hopefully it will come back later.
More info here.