Dai Vernon had something akin to that. I -assume- it was the serendipitous case you mention, but it is, after all, anecdote, so it might have been something more. But, pulling from Wikipedia - 'He also had an encounter with another up-and-coming young magician from his town, Cliff Green, who asked Vernon, "What kind of magic do you do?" Vernon responded by asking the boy to name a card. Upon pulling a pack of cards from his pocket, Vernon turned over the top card of the deck to reveal the named card and replied to Green "That's the kind of magic I do. What kind of magic do you do?" '