Identifying purchases without a vendor

ScoGo_Woodworking

Since adding a vendor is optional (but important for my needs), is there any easy way to easily identify purchases that are made that do not have a vendor attached?

I thought I could run the report of Purchases by Vendor and it would generate an "Unknown" entry, but that isn't the case. In fact, I specifically removed a vendor from one transaction to make sure and it just drops from the report.