IMHO, the OP's message is garbled. I don't think that the OP is saying that the cashier knew that they were a mystery shopper. I think that "Just write what happened lol" is just an instruction from the OP to themselves, and then a commentary (LOL). I trust that the OP takes greater care when submitting reports than when posting here.
@Shop-et-al wrote:
So... umm... how did the cashier know that you were a mystery shopper?
[My guess? Corporate/management has your name and image and all employees can id you when you arrive. So much for keeping the mystery in mystery shopping.]
Shopping Southeast Pennsylvania, Delaware above the canal, and South Jersey since 2008