The card was a reference (as if you couldn't have guessed) to my win in the Croquet tournament last week.
However I think that it should refer to the Royal Mail who managed to figure out to where it was supposed to be delivered.
As I am the only Edwards on the Island (as far as I and the Phone Book know) it should be easy enough to find me. Even easier if you have the postcode which one assumes was present before the letter arrived on the Island. But without my name and with only the tiniest other clue I think Royal Mail did rather well.