At the bottom of the gorge, the sparkle of a plant caught my eye. Not Shortia as I'd hoped, but nevertheless something that registered as "unusual". Like a trillium, though quite small, and not yet fully open. Heart pounding with excitement, I stretched as far out over the railing as possible, to get a good look. I continued on my quest, going twice around the loop, up and down all the steps, and down all the side trails, so I could pay attention to each side of the trail with my full attention, but no Shortia!
Back at the visitors center, I read the display on the federally endangered "persistent trillium" found only in and near Tallulah Gorge. It's called "persistent" because leaves stay on the plant into September, while most other trilliums dye back in summer. First success: finding a new (to me) rare trillium!
The next day, I went over to the native flora garden at the State Botanical Gardens of Georgia in Athens to confirm my identification of the persistent trillium. They have an excellent collection of trilliums, including a few labeled specimens of the persistent trillium which were in flower and looked exactly like the one I'd seen at the bottom of Tallulah Gorge.
For more info on the Persistent Trillium, read the Master's Thesis by Cassandra Plank called "Demography and Community Characterization of the Federally Endangered Herb, Trillium persistens: A study across its range including fire-dependent habitat. A link to the pdf is here.