My YouTube Watch Later Mystery Graveyard
jamesbvaughan.comTwo solutions I use to identify deleted/private videos in YouTube lists:
1) googling the ID part of the video URL to get/guess the title at least
2) https://web.archive.org/ (surprisingly it even has wholly archived videos for some URLs - random example: https://web.archive.org/web/20150111045309/https://www.youtu...)
I hadn't thought to use the internet archive for this! From a quick check on a few of the unavailable videos on my list, it seems to work well.
Thanks!