Why: One or more videos have been removed form the playlist because they were deleted from YouTube
If you saved a YouTube playlist you may receive a message a video was removed from your playlist because it was deleted. Don’t worry, YouTube didn’t randomly delete one of your videos, trust me. By default, YouTube will automatically remove any videos in playlists that were deleted from YouTube the next time the YouTube playlist is updated.
When you were editing the YouTube playlist, chances are you didn’t notice a video that was was already deleted (deleted videos show up as the white YouTube icon with three dots, pictured below). You probably didn’t scroll through the playlist to notice it originally.