What trillium is this? Ok, I'm not a botanist. But, after some research I feel fairly confident this a Vasey's Trillium Trillium vaseyi It is commonly called a Sweet Wakerobin, Sweet Beth and/or Sweet Trillium. The flower is pedicel and nods below the whorl of three leaves. The flowers are easy to overlook because they hide below the whorl.
You can find more information and photos of Vasey's Trillium at this website: