When I found a group of these growing in the grass I thought that they were St. George's Mushrooms. I then took a spore print and it was reddish brown rather than the expected white, so I then I thought I may have a toxic Inocybe instead, and lost all confidence in my ability of being able to recognize edible mushrooms... Looking through pictures, I was eventually able to figure out that it is actually an edible Agaricus campestris.
Ah, that's rough. Acquire a nose-for-hire through mushroom based bribery? But yeah, a pain not to be able to tell them apart :/