Think about it from a high level.
Mystery shops are a very small percentage of the interactions that an employee possibly could have.
What’s even smaller is the chance that an employee saw WOF and works in the place that this person is shopping AND they are the employee during the interaction AND recognizes the person conducting the shop AND they actually care.
I hate to ruin anyone’s parade, but the chances of us being discovered as shoppers are slim to none and if so, it’s a very small percentage overall.