I am a beast
what happens is....
someone finds it and puts it in the post.
More frequently with post cards - as with some other very rare events ( complete suit in one hand at bridge or even all four hands....) - it is reported more often than expected
and you would expect one suit bridge hands to be reported four times ( four suits geddit) more often than a complete 4-suiter and they arent
and even if all the worlds monkeys played bridge for the time of the universe etc....