My gf can play some of Miike Snows songs just fine, but when I try to play them, they're gone. Doesn't seem like a removal from Spotify to me - and my gf and I have the same subscription (I added her as a family member) and live in the same country...
This can happen when the song has been recently removed.
If your gf logs out of the Spotify app, and then logs back in, she probably won't be able to play it anymore.
Sometimes when a song is removed, it will still be playable for a short period of time, but then after a log out, the app refreshes the list from the Spotify server and detects that it has been removed.
I suggest contacting the artist or their record label to protest against the removal. The decision to remove it was made by them.
Not sure if this is the problem you are having though. Just my thoughts