Favoritos de plant_id_nut

I found this for still growing in a small stream in City Creek Center. I wonder if it grew here in City Creek before the Europeans arrived? Which makes me wonder if it came up after City Creek centerless constructed or it was planted there. I think it might be native to this area also so maybe I should give it the benefit of the doubt. What do you think?

Cap: cylindrical to bell shaped as gills liquify, shaggy texture, white to grey to black at edges as gills liquify, about 2” wide and 3-4” tall at maturity. Gills: close, liquefying from margin. Stalk: white, hollow, fibers at center, small bulb at base, up to 5-6” tall. No ring observed on the stalk, but a beige brown patch remaining on cap. Habitat: several clusters in grass in city parking strip.