FJ as a sportsbook has every right to cancel any match for any reason so long as they do it before it starts. You are not entitled to something because of it - had they done it when the game started or afterwards then you'd have a case here but as of now there is nothing. Bet was canceled BEFORE it was being played, what happened after matters not.
They might have the right to do it, but that doesn't make them not shady if they unjustifiably cancelled a bet. There's a reason sportsbooks don't cancel all bets that have had line movement against them.