What should I have done?

[Antonio.King]

What you did is all you can do since, as the R2, you're not permitted to blow your whistle on that fault.

There's nothing wrong with the situation itself. You indicated 4 contacts from your view, and your R1 disagreed and communicated with the coach post-rally that he/she had a touch on the block. There's nothing wrong with this.

What makes or breaks if you handled the situation correctly or not is what you responded to the coach with. What did you say to B's coach about the situation?