Quills just get everywhere, no matter what you do. My dogs are even stepping on them, the poor things. You can try lint rollers with the sticky stuff. They seem to pick up quills pretty decently.
Oddest place I have found a quill. On/in my pillow. Hedgehogs are kept in the living room... It was one of Winter's and that boy has some sharp quills. (I assumed Winter because it was small and extra pointy)