mox backup creates invisible files.

So I have a mox home directory and want to create a backup to pack it up and send it to a backup server. Naively, I run ./mox backup <location> as root, because all the other maintenance operations run fine as root...

...and end up with a directory that ostensibly exists (because when I run mox backup again, it says it does) but is not listed anywhere nor otherwise accessible.

How do I even delete it now?...