POR1 remaining quantities (even if OPOR is closed !)

Hi

How can I get the the total quantity received for an item in POR1 ?

Suppose I placed an order for a quantity of 10  on Purchase Order in B1.

I create the folowing Good Receipt PO

GR1, Quantity 1

GR2, Quantity 5

GR3, QUantity 2

POR1.Quantity shows 10

POR1.OpenQty shows 2

So far so good

then i close the PO. I know those 2 remaining items will never be received.

SAP resets the POR1.OpenQty to 0 !

If I rerun the query, there is 0 OpenQty.

So 2 months later I need a report of all Items that were incomplete.

I cannot use POR1.

What shoud i do ?

thanks