That’s quite unfortunate :( His channel is often the only youtube mirror of lots of good songs. So many links will be broken now… I hope he manages to get it back and set the videos back to public.

If you use a youtube playlist, it might be useful to periodically dump the metadata of it via yt-dlp or something, that way you at least have a record of which videos are in there if something like this happens again. I recall this happening sometime in the past with either him or some other uploader