You could always turn on the feature "show unavailable songs" that is located on your settings page but to be sure you can always get in touch with the customer services team directly using the online contact form and they will be able to assist you further with this.
If you get an automated email reply back directing you to the community or help pages, you need to reply directly to that email (even if its from no-reply) and one of the customer services agents will get back to you as soon as possible.
Alternatively, if you prefer support via Twitter, please tweet @SpotifyCares.
I´ve had this problem before with several artists and bands I've been listening to on Spotify.
Unfortunately it turned out that the tracks were removed from spotify by the record labels. The tracks/artist sometimes turned up again, but till then you might have to listen to your band elsewhere.
I hope this helped you!