I haven't had the disappearing object problem for a while, but I was redecorating the gym and placed six treadmills. When I went back to live mode, all the treadmills disappeared and a door as well.
I also found meals my sim had cooked in Granite Falls in the family inventory, and I can't drag to sell them. If I try to place them in world, they bounce back into the inventory. I managed to place one plate, but then when clicking on it on it to move it, it said "script unavailable" or something like that, and went back in the inventory. So now I have four different plates of food stuck there.