Found by my friend @graysquirrel. Thanks Krissa!
Second photo is a fruiting body from another log in the same location. I'd put that log in a moist chamber after collecting it in the woods.
I took this photo many years ago, but it is a noteworthy enough plant observation to be added to iNaturalist retroactively. There are very few records of this species from San Francisco and no specimens collected since 1962. Only days after taking this photo, the plants (5 in all) had been apparently eaten - nothing remained but holes where the roots had been.