Hey @emilyy_ky, thanks for coming to the Spotify Community!
Missing or unavailable music is almost always a decision by the artist/label to withhold the content from Spotify. Sometimes it's temporarily unavailable while they sort out legal issues or correct metadata, in which case it'll be back up as soon as they resubmit it to Spotify.
Please let me know if there's anything else I can help you with! Happy listening 🙂