Great little short story.
My thoughts and observations....

The intro was good, maybe because of the fact that the protagonist is alone. That made me wonder if something worthwhile was gonna happen.

When I read "but there was nobody there", it caught my interest. Even though the body of the story can be seen as typical erotica, it kept my interest. Partly because of the "nobody there" phrase, partly because it's well-written.

As for the ending, I did not know what to expect. But on reading it, I realized, there is no other way to end it.

Good work, and keep it up.