That's awesome Val! We've only found them in the yard once. My neighbor found 17 over the weekend growing in his tool shed under the tractor of all places! I'm going to go out today and see if there are any in my usual spots, I think that the cold nights over the weekend probably ended the season here but hope it didn't.
Good question. Any elm trees dying in your yard or nearby? The spores come from them and get blown around, in an open area it's possible, even in a woods we find them quite a distance from the dying trees. Also maybe spores in the mulch, I've heard of that happening before too when it came from companies that did mixed runs of lumber types.