PO Lines rejected back to req

I would like to know if this is standard functionality:

In July a large req was place on a PO and reserved, thus it was on our month end reports and in the Encumbrance Detail Report as an obligation.

In August, the lines were rejected back to the Req and the buyer deleted the PO lines that had been created in July.  (He also did an Unreserve action).  So to accounting, it looked like this large PO line obligation simply "disappeared".  This action did not leave any type of audit trail.  We had to check with the buyer as to what happened.  The correct GL entries were made, and our obligations were in balance with the GL.