For some reason, when I loaded Amarok today my collection had vanished. It was as if I'd just installed Amarok from new. I keep my music on an external HDD, and sometimes I forget to turn it on. I've done this before and Amarok hasn't done anything strange, just today.

After turning the drive on and mounting it, I told Amarok to rescan my music collection, but now it thinks I've never played any of my music before. All the stats have gone.

I'm storing the data in a MySQL database and do have backups, but why should the music suddenly vanish? I've just tried to reapply a database backup, but it's made no difference. How can I put it all back together?

This is Amarok 1.4.3 on Gentoo.