HiJane R.,
The work order is already completed so it cannot be changed. The transfer changed the serial number in inventory which achieved the same result as if you would have had the correct lot/serial number on the WO. Getting the lot/serial number changed on the WO would be more for your records as the WO has no useful purpose now that the item is in inventory and the WO is completed. If you really want the lot/serial number changed on the WO, you would need to update the tables using SQL statements.