Okay, here are the relevant rules from the Billiards Congress of America, who set the rules for the game available on FoD: (NOTE THAT CALL SHOT GAMES ARE FOR EVERY BALL, NOT JUST THE 8)
3.4 CALLING SHOTS
For games of call-shot a player may shoot any ball he chooses, but before he shoots, must designate the called ball and called pocket. He need not indicate any detail such as kisses, caroms, combinations, or cushions (all of which are legal). “Any additionally pocketed ball(s) on a legal stroke is counted in the shooter’s favor.”
4.2 CALL SHOT
In Call Shot, obvious balls and pockets do not have to be indicated. It is the opponent’s right to ask which ball and pocket if he is unsure of the shot. Bank shots and combination shots are not considered obvious, and care should be taken in calling both the object ball and the intended pocket. When calling the shot, it is never necessary to indicate details such as the number of cushions, banks, kisses, caroms, etc. Any balls pocketed on a foul remain pocketed, regardless of whether they belong to the shooter or the opponent. The opening break is not a “called shot.” Any player performing a break shot in 8-Ball may continue to shoot so long as any object ball is legally pocketed on the break.
It's not obvious, but if a player fails to hit the designated pocket in a call shot game it is NOT a foul shot. It is declared an "illegally potted ball", which just means that the person does not continue at the table.
4.13 SCORING
A player is entitled to continue shooting until
failing to legally pocket a ball of his group
. After a player has legally pocketed all of his group of balls, he shoots to pocket the 8-ball.
If the 8-ball is potted illegally pocketed, it is a LOSS OF GAME:
4.20 LOSS OF GAME
A player loses the game by committing any of the following infractions:
1. Fouls when pocketing the 8-ball (exception: see 8-Ball Pocketed On The
Break).
2. Pockets the 8-ball on the same stroke as the last of his group of balls.
3. Jumps the 8-ball off the table at any time.
4.
Pockets the 8-ball in a pocket other than the one designated
.
5. Pockets the 8-ball when it is not the legal object ball.