Almost stepped on this plant (one of only two found on our property) 10 years ago. The pic shows it dried inside my book "Trees Shrubs and Flowers to Know in British Columbia", C.P.Lyons. I will search again this summer for this delicate beauty.
If I may quote from the book: "The simplicity of this beautiful flower imparts an air of rarity that is further enhanced by its random appearance in drab range land. The stout stem carries one or more pale purple or lavender blooms often 2" across. The three large petals are marked on the inside with dark blotches near their base and a green band down their centre. One thin leaf grows from the base of the stem. The mariposa lily is seldom found in any quantity and often escapes notice because of its delicate shading...blooms during late May and into June. Range: Lower slopes of Dry Interior Zone, Penticton to Kamloops, Clinton, Phoenix."