Apparently, they do not like being reminded of their error. As a human, you can appeal this thing all the way to SCOTUS or whatever applies where you live. As a mystery shopper, do you want to make this one situation so noticeable that you lose anonymity?
Now that some time has passed, you might have additional options to consider.
You might thank them for this consideration. You could state that you understand that two versions of guidelines might have existed even though you do not now how that condition came to be. If you are brave, clever, calmed down, and/or a wordsmith, you might also ask them if the information that you have would be of assistance to them as they work to correct the glitch or other problem that resulted in multiple versions of guidelines for one shop. After all, your other work has been accepted and you have worked with the company for some time.
My garden in England is full of eating-out places, for heat waves, warm September evenings, or lunch on a chilly Christmas morning. (Mary Quant)