That sucks and all, but to be fair this is entirely on you. They sold you a DRM-Free file and you chose to not actually use it and to rely on their servers which you have no control over. This isn't a "DRM Free" issue.

Personal ownership means you take personal responsibility for it.

On Bandcamp you could have downloaded the files, the song could still be playable and you would still own it. DRM-free just allows you to download stuff so that if anything changes in the future you still have the original available, anything hosted can be changed at any time in order to stay out of trouble as a site owner. It still sucks that this is happening though

If you buy something DRM free, you must keep an offline copy. They can take away the option to download it, but they can't prevent you from playing the copy you already downloaded.