I think the anemonellas are what Kristl calls "ephemerals" by which I think she means they are here today, gone tomorrow, quite a short season above ground. The seed too, when there is any, has a short life compared to many others, as with many Ranunculaceae.
As a reassurance Rob, you could (very gently) feel below the compost surface and you'll surely feel little hard, knobby bits, just waiting for next year.
