Calochortus minimus goes by Star Tulip in Botti and the Laws Field Guide, but it is also commonly called the Sierra Mariposa Lilly. It is indeed a Mariposa Lilly (Calochortus) so that name may be more appropriate, but I prefer to follow Botti's nomenclature.
I see the occasional star tulip most years, but the summer after the Telegraph Fire I saw them almost everywhere I hiked. According to Botti, they are rarely flowering, so seemingly uncommon, but a large bloom was found on the edge of Big Meadow after the 1990 A-Rock/Steamboat fires. That suggests that my experience in the year after the Telegraph Fire was not coincidental.
C. minimus can have white anthers, but as you'll see in the pictures it can also have blue/purple anthers according to Jepson. So the color is not particularly useful. Normally, of course, you can count on there being three or six petals in any member of the Lilly family. C. minimus is no exception, but if you look at my pictures, you'll see a mutant four-petalled specimen. I have no idea how common that is, but if you look closely at the photos you'll see that the flower on the same plant had three petals. The leaf is plainly visible and you can readily see that it is indeed a monocot (or at least a plant with leaves that have parallel veins, which for me means monocot). So I'm fairly sure of the identification. I'm also sure it's not some strange sepal pretending to be a petal. If you count the stamens, you can see there are eight of those. Normally C. minimus would have three petals and six stamens.