So, my laptop is at the manufacturer's being fixed, but I retained the SSD.
Just now, I accessed my SSD from a different computer, and my home folder was missing. And /var was empty.
Weird.
@light Sounds like you have just the mountpoints for /home and /var, despite the assertion that everything's one encrypted root partition. Perhaps you might understand more by inspecting /etc/fstab and seeing what, if anything, is supposed to get mounted over those two directories?

@bojidar_bg
I'll try that.

Come to think of it, it could be on a separate btrfs subvolume. What would I check in that case?

@light My btrfs-fu is a bit rusty, but `btrfs subvolume list path-to-mounted-filesystem` should do the trick, probably with the -a flag.
@light did the laptop have sata + m.2 combo? base system on d0 other directories on d1.
@Woodlander
I had the entire root directory on a single encrypted partition
@light ok. If it's a LUKS volume, you'll need to mount it with the <cryptsetup> command. the graphical installer makes it easy to setup. learning how to recover it manually is an effort.
@Woodlander
I just clicked on it using the Cinnamon file manager on the other computer and typed in my password.
@Woodlander
Every folder had the expected files in them other than /var and /home/me