If an order disappeared from your Orders > Unfulfilled Orders page, this order was either canceled by the customer or placed under review. You do not need to fulfill this order if it is no longer in your Unfulfilled Orders queue.
When an order is placed under review, that means that our Fraud Detection Team is checking to make sure the order is valid and authorized. The Wish Fraud Detection Team both automatically reviews all orders for potential fraud and manually reviews all high-risk ones for potential fraud. Any orders placed under review should not and will not need to be fulfilled.