Delay on B?

[don't move]

Funny, I had this happen in a varsity game just this past Friday night: Score is tied 28-28 with 15 seconds left in the game. Neither team has any timeouts left. 1st and 10 on B's 30. A spikes the ball, I kill the clock, signal to HL that it will be 2nd down, down holder is having problems with the box which HL is tending to, I look up and see the head coach of team A (HL's side) and a water girl headed to the middle of the field! No one called time out, there were none to give, apparently the coach thought spiking the ball gave him a time out. I immediately ran him back, told him there was no time out, he was fine with that, but team B's coach was livid. I did not throw a flag. B's coach was mad at my LJ for not flagging the coach all the way across the field, for being out there, and of course mad at me. I explained to B's coach that it was our fault that A's coach was coming out on the field, that he gained no advantage since he never really got to the huddle, (although he was at about the hash marks) and that I was going to let the kids decide who wins the game and not let the outcome be affected by our mistake. B's coach wasn't happy. (Team B won in 1st overtime). How would you guys have handled it?