Hello Scot, 

Those both fields (property_account_payable,property_account_receivable) are kind of fields.properties which is one kind of functional fields. Those values being set by system at runtime by company wise ( multi company scenario ). so you can't see those field inside the database or neither their values on res_partner table.  

If you want to see those values, you can find them over this menu. Settings >> Technical >> Parameters >> Company Properties. 

Filter out on "Resource" like it contains "res.partner" and you will get Property Account Payable & Property Account Receivable for your specified partner ID. 

In order to understand methodology of fields.property you can visit this link

Hope this helps,