I looked at the letter and check it contained and was confused. The sender lived at our old house - the one we moved from after Frost's first year.
I called the author of the note. Indeed, she lives in our old house and remembers us moving on. The gate that was installed for us is still unfinished but they are happy there.
She meant to send the note to a friend who lives a few doors up from us but reversed two of the numbers by mistake.
Peculiar? Downright odd.