Is there a way to identify if a price on a PO defaulted from a BPA or Price List?

We have a requirement that purchase orders where the price is not setup on a price list needs to go for certain approval (we are in the process of implementing AME). Is there an easy way to identify the source of a price on the PO? We currently use a mixture of blanket purchase agreements and price lists to maintain pricing.

A few fields I've found but did not work are:

MARKET_PRICE - Checked this and it is null

LIST_PRICE_PER_UNIT - Shows the price defined on the item level and not the price list or BPA, we don't maintain price on item level so this is always 0.