RTV Inventory/AP Vouchering Issue

Not sure if anyone can help with this, but we had an issue with AP having open vouchers for RTV POs that were not even recevied from the vendor yet. So it would stay on oiur received not vouchered report for weeks before we found the issue or received the credit. To avoid that, we created a process the show the RTVs open until a credit memo was recevied, but this is causing the RTVs to show invnetory in locations where the products were already shipped back to the vendor. Do any of you have a better process?