OP- completely understand.
I haven't had many that require the reveal, but the ones I've done where I had to call back and cancel the appointment and announce it was a mystery shop weren't as fun. The disappointment (or anger) in the person's voice on the other end was palpable for all but one who laughed and breathed a sigh of relief because she was already trying to confirm my info and having trouble.
In those cases, I just prepared myself with exactly what I was going to say, slapped on a smile before I dialed, made sure my tone was professional and friendly and wished them a good day no matter how they responded to me.
While I have done quite a few phone evalustions, I don't take as many anymore.
Reasons:
1. In my experience (except for a handful a scheduler gave me as a reward for helping her with a last minute re-shop 50 miles away), phone shops are just as much work and take just as much time as an in-person shop that pays much higher.
2. It seems the phone shops usually get picked up quickly, so I feel like I'm wasting my time to even click through the links.