Standard Purchase Order in 'Closed' status without receiving with 3-way match

Friends

I have an issue in production where a standard purchase order went to closed status even without receiving with match approval level as '3-way'.

This PO is now in approved,closed status. When i look at receipts the receiving is not done. Invoice is created but the invoice is not paid.

It would be very helpful if someone can help me with the possible reasons for this to happen.

Thanks