We have a Lowes in the town I live, Does anyone know EXACTLY what to ask for/look for.
Some might refer to them as Saltillo tiles, others as quarry tiles, still others as terra cotta tiles. Names seem to be more of a whim of the marketing department than anything else.
The key is the first word in your title: unglazed. Ask a salesperson for assistance if you don't find what you need. The Lowes' staff seem to be fairly knowledgeable about the products they carry, although they probably won't have a clue if you tell them "I need a tile I can put in my oven to bake bread on."
Hope that helps.