I've only been mystery shopping for a few months, but I've ran into people I knew two times.
The first was at a woman's exercise clothes store, where the dressing room attendant was a woman who teaches classes at my gym. She asked all kinds of questions about my exercise habits and how the clothes fit into into those habits.
The second was at a drug store where I saw a woman from work. She's pretty nosy and tried five different ways to figure out what I was doing there. I made a generic response and went in the other direction as fast as I could!
Happiness is not a goal; it is a by-product. Eleanor Roosevelt