The story (rather than the event) reminds me of a customer I had when working retail. The day after a significant purchase, one that took a longer time to close than most, the customer returned to the store with a dry look on his face. Immediately, I went to meet him thinking uh-oh what happened...what am I in for today?
The customer, without blinking looked straight at me and asked "do people usually come back the next day to tell you they are happy?"
I answered, "usually not."
He said, "Well, I'm one of those people. I love the (product), its amazing, thanks for the recommendation and service."
I was flabbergasted and more than a little happy. In fact, I've used this method a few times as a customer.
Thank you for posting and reminding us that its good to give a pat on the back when things are well done.