Catholicism is not sola scriptura. 

The Catholic Church takes a more comprehensive ear to the will and word of God, looking at revealed teaching (Scripture), natural law, rational inquiry, etc. 

The approach you seem most comfortable with is a fundamentalist one: "where in scripture does it say this'.  That's not the Catholic approach to leveraging Scripture. 

My checkmate move to you is:  where in Scripture does it say we only believe what's in scripture!

Show me the verse and I will cede.