Material lying with subcontractor

All SAP Gurus,

We are using subcontracting PO and with reference to those PO sending the material to subcontractor.

Then we make the GR against the subcontracting PO.

Some stock always lye with the subcontractor.

How to know the document numbers (transfer posting documents, Movt type: 541) against which the material is still lying with the subcontractor?

Note: we are not using Batch Management.

Regards,