(I'm cross posting this for people who may have issues with the judge forum)
Ouch. Situations like that are unfortunate.
The first thing to do is, like Anthony said, to investigate to see if the random person making the statement knows anyone in the match or if the statement was purposeful or solicited. Assuming that no malicious intent was involved and the player just didn't know how loud he was ... we do nothing to the gamestate.
Yeah, that sucks but nothing in the gamestate is illegal and none of the players made an error. Explain to the players how unfortunate it was and have them move on.
We certainly take the spectator aside and have a stern talk about interfering in a match, even accidentally. You can certainly award the spectator a Unsporting Conduct infraction, even entering him in the tournament to do so if he has a UDE number. This will, at the least, let us see if he's done this sort of thing in the past and monitor him in the future.
Erik Mock
UD Judge Coordinator
WoW TCG Rules Knowledge Level 3
Player Management Level 4