OK, I believe you. Could you post a photo so we can see what you mean?

Well, I did a quick surf and I agree, this is a lovely species. Can't speak of regional differences, but from the photos it's lovely. I guess I've never been quite far enough west to witness this one in person, but I've seen most of the Appalachian species. Here's a gallery of Trillium species, including T. flexipes.

Here is a link that might be useful: Trillium gallery

The trillium bible is "Trilliums" by Fred & Roberta Case.
Coryjames' post sounds like a quote from page 100.
Along Maryland's Susquehanna's River we have some variation of T. flexipes. About one million will be blooming next month. As the name implies, the flower is bent or reflexed. The petals are ivory and heavily veined and the base of the petals do not overlap. The leaves are large and heavily textured. The ovaries are white, purple or striped. Anthers are greyish.
T. grandiflorum can also be variable. The ones that I have seen are more refined than the above. The flowers are not reclined. The anthers are golden yellow. The base of the petals overlap. You just about have to pull the flower apart to expose the ovary. There is a tiny, protected population of T. grandiflorum f. roseum on the Lancaster Co, side of the Susquehanna which is exquisite to see in bloom.
Those of us who observe trilliums know that the pedicellate ones hybridize freely. They are incredibly variable.
Sam