Slightly off topic, but similar. Every now and again, my sim will cook a meal, but, on completion it simply disappears. As to the missing items from inventory, I don't know if it is worth trying, but, pressing the up or down option may bring the items back if your game is paused when you move the item. I have noticed that if you delete an item then press up or down, then return to the original level, the item returns. As soon as you leave pause, the item is gone for good though.