Bet on it: which came first?

As Jon went for breakfast he saw Zoe sitting at the kitchen table flipping through the newspaper. She looked up as he entered. "Oh, is that the wishing rock you won? Can I have a go with it? There's this annoying boy at school I want to make forget about me." Jon was flabbergasted. Then his second memories floated through his head and he remembered winning a bet on the outcome of a Tv show they were both into. Zoe had wanted the power to shapeshift and Jon had won a stone that was as powerful as the bets but without the chance of losing. But if it had happened like that, then it was a paradox! Which came first the wish rock or the bet?