@Mikezumi the inventory and relationship disappeared after I needed to reset a lot with Master Controller, but my sim wasn't there at this time. It's a rotating save and I usually don't have any problems with it whatsoever, but oddly enough, when I've gone back to my original family, their relationships were a little messed up, too, but their inventories didn't vanish completely (Lucky enough I was able to set their relationships back how they should be with Debug Enabler). It's good that I don't have any bigger problems with my save though.
And no, I didn't forget to save @Charlottesmom , I didn't save at first after the glitch happened, so the in game time actually has gone forward, but solely my sim was like one week behind with everything, that's the funny part :D
ETA: I think the only things left in her inventory were things like a camera and her diploma, the things that are there from the start of the game anyway.
