Here are 2 strategies:
1. Call the violation. Then check with your partner about who touched the ball last. If your partner knows it was A, then you made the right call. If partner doesn't know or it was B, signal accidental whistle and give the ball back to A.
2. Don't call what you didn't see. If partner saw a BC violation, let partner whistle it from the bowels of the FC.
Neither option is appealing. Try to see who touched it.
