I have had something similar once, this was pre internet days. I had answered an add in , I'm sure it was the sport, for a married woman looking for no strings fun, it was to be a car meet. She was driven to me, by her partner, upon reaching the agreed place, she got out and into my car, where we spent a good 45 minutes, after we had both been sated,we went our own ways.
A week later I got a call asking if I had anywhere we could go and she would like her husband to join us and I could bring a friend also, she was looking for a mmmf, since it was a same day thing, couldn't find a friend, so it was a mmf. She introduced me to anal, she wanted double penetration. No money changed hands.