Skaha Bluffs east trail
I checked back to my observation of https://inaturalist.ca/observations/26152273 Parthenocissus inserta and settled on P quinquefolia here because the leaf edges are less densely "pointed". There was just this one lonely seedling on the peninsula so if it's quinquefolia it could be the result of a bird's visit to someone's garden.
This plant is new to me. Leaves are quite large: 10 to 15 cm approximately. Being eaten by that caterpillar I didn't see at the time. No sign of flowers. The closest leaf I could find is that of the Pacific Waterleaf but I don't think I'm right with this identification. Thanks for considering this.