Pain de Mie (sourdough)

Not sure how to rate this - the dough itself smelled great, even tasted great, my starter was ripe and ready, \ but somehow my dough went from a beautiful, supple ball to a weird, sticky puddle. It did not look overproofed but I'm guessing that was most likely the problem. In the end I took the dough, divided it in half incorporating one half into pizzas/focaccia using the recipe in the Wooden Spoon Bread Book and the other half into Perfect White Bread (p 71) in the same book. All came out excellent- rose perfectly with great flavor! The real lesson here is that overproofed sourdough can be resurrected!