there has been a sporaidic error, that periodically will either remove an Item Code from the MTICMSTR or BKICMSTR. ( sometimes it duplicates too)  
no matter, use Maintain Database, check to see if the Item Code exists in the BKICMSTR. if it does, you can go back to IN-B lookup and review / edit the information and save. the record will be updated in the MTICMSTR.