Thanks, Yes, I found them, and it seems that MC took an automatic backup of the Library from when I launched the program this morning, so it appears I lucked out!
ALSO, regarding the curiosity of the missing libraries after the (bad) restore... I left the box checked for Restore Settings, and I'm guessing that was the thing that killed off MC's memory of those other libraries. After I restored Main from the auto backup, I then carefully and correctly restored the Karaoke library, and Unchecked the Restore Settings checkbox, and all the libraries were retained in the list of known libraries.
Cheers,
Jeff