[MayflowerMadam]

“send this back, if you no longer live at this address”

Is that anything like, “If your phone doesn’t ring, it’s me”?

[Verginius Rufus]

It reminds me of a line from A. E. Housman's "Fragment of a Greek Tragedy":

"If you happen to be deaf and dumb, and do not understand a word I say, then wave your hand, to signify as much."