You have 2 options:
1. Call CSC and give the order number and ask them to cancel said order
2. Put the item in hold but make sure to keep track of the order number. Go to the MyGO app and search for the last four numbers of the order number. Tap the guest order and tap the quantity number for the item. Choose other and say couldn’t locate, unfulfilled, etc and put 0 for the new quantity.
3rd option if you haven't tied it to cart is forceclosing app and then going back into batch after subtracting item from BR location.