How to change the default Buyer on PO

Hi,

When a user is creating a PO and selecting a vendor, the Buyer field is getting defaulted to another user who has left the organization. We tried to change the Primary Buyer in the Item Categories and Item Purchasing attributes. We even update the Primary Buyer in the BU attributes in Item Categories but still when the vendor is selected on the PO, it is changing to old buyer. Is there any another place the Buyer is setup and do we need to run any process after updating the data?

Thanks,

Kula.