The Play that goes wrong question

Yesterday i saw the play that goes wrong again after seeing it once during previews and i noticed something very different that happened but I'm not sure if it was supposed to happen. When the inspector is supposed to not be able to find the book i heard someone from the back of the audience yell "Its under the couch" and i thought that it was someone who just thought it was a rude person who decided to ruin the joke and yell it out when suddenly a bunch of audience members started to yell the same thing at him the inspector then got up and (completely in character) yelled at the audience for laughing at him and calling out people in the front row and such and then sat down upset and found the book. It seemed very scripted and i was unsure if maybe this happens a lot and he had a bit planned for when it happens or it was a new thing added to the show or perhaps he improved the whole thing. Has anyone seen the show lately and knows if this is a new joke in there?

Alex M- That was aded right at the end of previews. The audience members are not plants, and he will push and push the audience until someone finally yells that it is under the couch. (The first time I saw it, someone yelled the ledger's location fairly quickly. The second time, it went on and on, with a great deal of improv by the actor to push the audience into participating, until someone mid-orchestra yelled the that it was under the couch.)

So, in sum: it is scripted, but requires improv to the extent that the audience has to be pushed for someone to yell out that the ledger is under the couch.

I saw it in April and no one from the audience spoke up.

Saw it in previews, that bit was in. Took a few minutes before an audience member (from the front) called out. I think by now people likely know about the bit so are more enthusiastic to join in calling out its location.

I'm pretty sure some of the swag they sell in front has "A LEDGER?! A LEDGER?!" printed on it.