Undo radio calibration??

[jrward05]

Just started my daily mix and got curious about the button that is a circle with a line through it. I clicked it and it said it won't play that song anymore, but I like the song so I wanted to undo! Then I clicked the bar at the bottom saying never play this artist again (yes, intuitively I realized it would probably happen, but my hope was that it would ask "are you sure??" or give me somet other options). So now my playlist will never play one of my favorite artists which is precisely the opposite of what I want to happen. Where's the UNDO??? I was just trying to learn how to use this new feature and I got screwed... Come on...