PO Final Closed, did not release unfulfilled demand

HI - hope you can help.

We have a PO that was created with NO REQ, and matched and invoiced and finally closed. PO was for 1.4 million, AP Invoices matched for 1,382,892.00 leaving 17,108 that should be released back to budget, but this did not happen.

Is this because the PO was manually placed in Final Closed Status and this does not release the funds?

Since the PO is matched (2-way Match) to the AP Invoices and all AP Invoices are paid, could we reopen the PO (this is allowed now) and cancel the PO or the lines and make sure the cancel unfulfilled demand = YES?