do you have any idea why they keep disappearing? I've noticed this too and it's really strange
Not sure, but I think it may have something to do with the way the autosaves are performed; it seems like ownership gets attributed to the hosting ID (38k something) I purchased specifically for that purpose. So, when people load up additional saves and start clearing out any clutter that gets loaded with it, the main bricks get cleared by accident.
Wasn't there a wand tool that let you set the ownership of bricks? We could really use that if we have to keep loading backups. In the meantime, I encourage everyone to make a save before they leave the server each time they do. Just as a precautionary measure.
It's important that everyone can feel confident knowing all their hard work isn't just going to disappear.