i never heard that before but in my understanding. . .
the direct object is a pronoun!?
a direct object answers the question WHAT?
Mrs. Sipi bought a gift for his husband.
so, Mrs. Sipi is the subject
gift is the direct object
and husband is the indirect object!
-to get the direct object(D.O) the formala there is verb + what
so, bought what?
gift, so gift is the direct object
but some sentence have no indirect object but have direct object!
but there is no sentence that have indirect object w/o direct object
hope i answer the correct question!