YES! It's so unbelievably annoying when websites just remove stuff from your playlists / bookmarks / whatever without telling you what was removed.
For anyone stuck in this situation and willing to spend a few (many) hours to recover the titles of their YouTube playlist:
On the playlist page, in the (...) menu there is a "Show unavailable videos" button.
After clicking that, you can right-click all the unavailable videos and copy their URLs. Then you can either try the wayback machine, or google the video ID. Usually you will find some forum posts talking about the video and mentioning the title.
Of course, it's not guaranteed that you'll find anything this way. But I have recovered multiple playlists this way.
hmry|1 year ago
For anyone stuck in this situation and willing to spend a few (many) hours to recover the titles of their YouTube playlist: On the playlist page, in the (...) menu there is a "Show unavailable videos" button. After clicking that, you can right-click all the unavailable videos and copy their URLs. Then you can either try the wayback machine, or google the video ID. Usually you will find some forum posts talking about the video and mentioning the title.
Of course, it's not guaranteed that you'll find anything this way. But I have recovered multiple playlists this way.