Comment 6 for bug 87089

The sqlite database is stored at ~/.kde/share/apps/amarok/collection.db, but others like postgresql and mysql are stored wherever you have the server set up. I wouldn't think upgrading packages in feisty->gutsy or other would clear that, but to be honest, I'm not really sure why this would happen.

It's difficult to troubleshoot without running a bunch of upgrade tests. Losing covers, which are stored in ~/.kde/share/apps/amarok/albumcovers/*, may also be from something going on in the database not realizing that covers are available. Sorry I can't be more of a help.