Thanks - we're aware and I'm trying to find the backup from SF database to restore. Is there something different about the ones that remained? Were they private/public/restricted, locked/unlocked, inside a town etc?
Unfortunately the way they set up the data storage means we cant get at a backup. As we can't guarantee that this won't happen again I'm going to remove BSUs from the crafting options of Sensible Toolbox.
Ok, thanks RA, The only thing I really lost was a full BSU of ender pearls, some redstone, and cobble so I feel fortunate. Now Veyron is another story, I think the majority of his hoard were in BSUs. If you see him, you should ask him what he lost.