OSP:PO return un-applies zero transactional value

We are on 12.1.3 and use outside processing process.OSP resource is costed at actual(standard is unchecked),OSP item linked to this OSP resource is of type assembly .OSP PO was created for qty 1 and has a price of 1 .

On PO delivery the value applied to the WO was 1(PO qty times PO price)

but on PO return the value that was unapplied shows zero and not 1 .No chnages have been done to any of the setups between delivery and PO return.

We tested this with another work order with same OSP resource and same results.Why is the PO return not un-applying a value of PO qty times PO price  instead of zero?theOSP resource  qty on the other hand applied and unapplied is same and is correct