I don't think the SSD is corrupt, Windows scan finds now errors, and it's readable. And it's unlikely both would get corrupt at the same time.
However, the SSD appears to be Readonly (and says so under Ready Boost property, not that I was going to check that off, it just says device is mounted readonly). Said the same w/ the thumb drive, but now it doesn't after using Eject.
I managed to find Eject for the SSD, but it didn't help.
Might just reformat it, and restore the backup. And never remove it from the Pi w/out shutting the Pi down.