My sourdough starter was dead for two months and I didn't know it

I feed my starter every morning before work and about two months ago I noticed it stopped rising much, so I figured it was just the cold kitchen here in Albany. Last Saturday I finally split it in two jars, one I kept feeding white flour and one I fed rye, and the rye one doubled in 4 hours while the white one just sat there like wet paste. Turns out my white flour was old, like a bag from August that had gone flat, and I'd been baking bricks with it for weeks wondering why my loaves had no spring. Grabbed a fresh bag from the co-op and the very next bake came out tall and open. Has anyone else had a flour bag go bad on them without any smell or sign?