CREATE TABLE table_name_89 (missing VARCHAR(255), unit VARCHAR(255), killed VARCHAR(255), wounded VARCHAR(255))
How many of the Royal Waggon Train Unit were Missing while having a Killed of 0 off 0 men and a Wounded of 0 off 0 men?
    
SQL: SELECT missing FROM table_name_89 WHERE killed = "0 off 0 men" AND wounded = "0 off 0 men" AND unit = "royal waggon train"