Mystery Monday: Her Voyage, Part IX

A snapping twig, or something, drew away
My keen attention on my sister's tete-
A-tete with that strange monster. I can't say
What happened, that split second. Such is fate:
We miss what we'd most dearly like to see
Because our hindbrain thinks all things are threats
That do surprise us. So then, only me
Would others notice where I stood. It gets
Yet weirder, there at my dear sister's place.
The shark and she, they both had disappeared,
Odd ripples in the dirt the only trace
Of either. Late that night, I got a note
At my hotel. "So long" was all she wrote.