To quote Connor:

The disk had a complete and total breakdown with next to no advance warning.
I got a "disk will fail within 24 hours" warning, but by the time I made it back
home with a replacement disk, the old one was completely dead.

So, the reason the FTP is empty is that it now has a new disk. I tried
some recovery tricks on the old, but it seems to be a pretty terminal
problem that I think only one of those (hugely expensive) recovery
companies could work around.