Found growing creekside in a shaded ravine with filtered sunlight. There was only the one stem with no other off shoots near by. Interestingly it is growing underneath a very old and declining Pacific Yew. I have searched all the native plant lists and skimmed page by page through "Plants of Coastal British Columbia" with no success. Any ideas?
How about page 102? The line drawing looks more like your plant than the photo. Looks like trillium and in this region, it should be Trillium ovatum.