Valley of Sighs

There I was waiting for Pist to come down the road to open the gate so I could follow him back up to the house in Beaumont Antire.
I'd lost my key to the lock but instead of getting a new key cut last fall or allowing me to just replace the damned lock he has to drive the quarter mile down the road.
I did a lot of eye rolling and unambiguous sighing. Pist is my long suffering, sporadic (I do like my space) partner and Daddy to Bellie.
Bellie is cool. She never mentions her other Daddy.

Pist is the first syllable of his last name.
When we first met - I had stalked him - he had told me he'd been called Pist since he was a kid.
I would see him at the Y. I'd be on an elliptical and he'd be on the track.
I was bored so I watched him and invented an elaborate story about him in my head. He was easy to watch.
I really wanted to talk to him so one day, as he walked by me, I said, PSSSST!
PSSSST, I said again. He turned.
Confused, he asked if we were acquainted because, unknown to me, everyone called him Pist.
Since he was a kid.
Which sounds like PSSSST.
According to him.

I discovered the story I invented about him was accurate the second time we talked.
He is a scientist and a pianist and resides in the house that he had built into the bluffs near the confluence of the Big River and the Meramec River.

Update 1/9/21. Text received this morning: Madam. You've neglected to mention it's the 4th key you've lost.