I can't think of a specific rule to apply here, it's just a matter of the TD's judgement and degree of leniency in these situations. Personally I'd probably hold this player to the check as originally called more often than not. If it's serious enough to give the guy a one hand suspension, IMO it's serious enough to call it a check. The fact that the dealer has changed his mind doesn't hold that much sway with me, I'm more concerned with his original impression, which was that A had checked. Then you also have an issue of semi-substantial action here because B has shown his intent to bet in this situation (albeit he's relieved from that action here IF player A bets). I don't like the idea of "rewarding" Player A's ill-timed gesture with knowledge of what Player B would like to do. Player A will be more cautious with his hand gestures next time.