By today when I watered the cap had broken off the stem but I made a pic anyway.
Searching tonight how to make a driftwood heart, I ran across a site where somebody asked about mushrooms in their houseplant pots and there were my mushrooms!
Leucocoprinus birnbaumii, aka Lepiota lutea, the yellow houseplant mushroom.
If you want to know more about this common houseplant mushroom Tom Volk will tell you all about it.