Camp question

[Scrapper1]

So I just got home from my second volleyball officiating camp ever. This was a PAVO camp with great observers. It's really just a 24 hour camp with a classroom session on Friday night and then two observation sessions on Saturday (each session includes one observer watching you work R1 and then R2).

I would've enjoyed a second classroom session, but even without it, it was a very good experience.

Here is a situation that actually happened to me and the clinicians were divided on how it could be handled. I'm R2 in this play.

A1 attacks the ball and B1 shanks the first team contact so that the ball contacts the curtain/divider that separates two courts. The first referee does not sound the whistle and allows play to continue. Can the second referee blow the whistle to end the rally?

R2 is allowed to blow the whistle when the ball is down, in or out, right? But does that also apply to a touched ball? If not, is the curtain considered to be a wall (which would mean the ball would be a touched ball hitting out of bounds); or is it a non-playing area (which would be "out" when the player plays it, which the R2 can whistle)?

OR. . . is it not actually covered by rule at all? Is this simply an officials' procedure? In which case, the situation would not be protestable, regardless of the R2's decision.

What can/should the R2 do here?

(In my actual situation, I didn't blow the whistle and the observer was directly behind the R1, saying "Blow the whistle! Blow the whistle!", which she did. Please don't bash the R1 -- she is a first year official and just froze.)