Local Files Issue

[Forfaren]

I bought a demo for a song i really like, it was named the same as the official release. The demo overwrote the music file which was in spotify, which meant if i were to listen to the official album the track would be swapped out with the demo. i tried the web app and my phone and I could listen to the original track there. I tried renameing it with the following (DEMO) at the end to maybe separate the two tracks. As a result i got the message "This song is unavailable. if you have the file on your computer you can import it".

I would apreciate help with recovering my ability of hearing the original song.