consume a material not avl in the PO component of PO

Is it possible to consume a material not avl in the PO component of sub-contracting PO ? Subs-adj does not allow addition of item . Such a situation arises when the supplier completes the job with an alternate material avl with him which has been issued for some other PO without correcting the PO components. The consumption of this alternate matl does not happen instead the original matl(not issued for this po) gets consumed in system. This mistake happens since the volume of sub-contracting operation is very high.