If items disappeared from your cart, a customer’s cart, etc., then it is likely because the items in question had some change(s) made to their product options. Unfortunately we cannot recover the cart’s previous state after this happens, you or the customer will just have to add the items to the cart again. We are so sorry, this is an unfortunate side-effect of using BigCommerce but there isn’t much we can do to prevent it as these types of changes are typically high priority for us to ensure that our products are always up to date.