You can log into the Microsoft website and obtain the unlock encryption key from there (dealt with that before.)

And Microsoft isn’t the only one who updates BIOS with system updates. I’ve once had to deal with someone who’s Macbook wouldn’t see any drive (and so couldn’t load into macOS, or even re-install the OS). After a lot of back and forth had to finally find out that during an update they were in a hurry and forced the machine off and it was saying “Firmware update in progress”, but they assured me that couldn’t have been the issue…