I did that thing on my laptop where you update your BIOS but forget to write down your BitLocker key... On a previous machine I was able to recoveer from this by installing the exact BIOS that I had before the upgrade, but I didn't write that down either. Extreme fail.
Luckily I had transferred important stuff to my desktop long ago and only used my laptop for browsing. (And I do keep the BitLocker keys and triple backups for my desktop.)
Still. What a pain.