Interesting..! I've had something very similar happen on Fedora running btrfs, too.. No hardware failures (drive was great, still run it to this day a year later), no kernel panics, the partition just stopped booting out of the blue, with the rescue shell also being completely broken. I think I almost managed to get some of my files back, but after an error on my part it corrupted itself to the degree where the only answer you could find online was something like "just give up, no one can help you now :(". Lost a bunch of important data and still a bit mad about it, but at least now I'm back on NixOS with ext4 with no issues so far!