Three times now my friend and I have had to restore our game from a standard copy one of us thankfully made because hours of playtime was erased by there being no save or backup saves created during that whole session. This latest time, it was him who owned the shared world. I had played through 6 in game days, a couple of them with him. During that entire time, not one save was made, even on logout when it says it is going to make a save. I had made a standard copy when I left the game since we flat out lost everything from our first game and we didn't want that to happen again.
I'm not sure if making the standard copy somehow made the shared save lose all those hours of gameplay or not, but that was kinda crazy that neither him or I had any trace of it otherwise.