Personally during the game as it happened I think he definitely heard the whistle. Watching it on replays I'm not as sure, but I don't think the time elapsed is that valid an argument, as it doesn't take long to kick a ball anyway. I think it was a harsh yellow, given that refs normally become more lenient when a player has been booked, they don't like to issue a second yellow for something soft.
The Arsenal whining is annoying though, he had 55mins to do something, yet he did bugger all. Plus he had been injured, so probably wouldn't have lasted the game.