I'd be inclined to call it 0-1 (win to Player B) unless the club is habitually strict on not reporting results - although as he left the tournament it doesn't make any difference if it's 0-0.
* If the game has already been lost by Player A in regulation fashion then post-game shenanigans shouldn't change that, as it affects other players. It's not clear that Player B was resigning anyway, it may have just been an annoyed reaction to A's ungracious attitude. Had B instead said something like "Get stuffed" then I imagine A would have been less keen to take him up on it.
* The manner of reporting results is not a FIDE law but a local admin procedure. In general arbiters in not especially serious events aren't too pedantic about how they find out results.
* FIDE laws state that a player whose time expires loses. If expiry can't be established then the status quo (game continues) is the sensible interpretation. But while the laws identify circumstances where expiry is unarguable, they don't state the converse.