Removing the link between a PO and a PO Receipt where all items on the PO Receipt have been returned.

I have a PO that was setup with the wrong Vendor.  I received an invoice for the PO and created the PO Receipt before I realized that the Vendor was wrong. 

I did a Return of the PO Receipt (essentially nullifying the POR).  This Return actually created a second POR which reversed the first one, so all items on the PO are back to “un-receipted”. 

I want to correct the Vendor on the PO but since there is a link to to the “received” POR and the “returned” POR, the system won’t let me change the Vendor.  I get an error message saying - “You cannot change the vendor for this purchase order because it has purchased receipts linked.”

Is there a way to remove the link to these two PORs to the PO?