The "Locked-In" Story

So I have this story...

I wrote it probably 3 years ago now, maybe longer.  I had an idea, and wrote a 3-part story for it.  Now, it's not a super-long story.  I have a minimum of 40k words before I'll consider publishing a book.  This one is about half that.  So it doesn't meet my own requirements.

The story is condensed, without a ton of extra detail.  So, I can rewrite it to be more detailed, but that's not going to put it anywhere close to my requirement.

I can possibly include some extra details, maybe expand on a character or two, to make things fluid from part 1 to part 3.  Again, this will add to my word count, but I'm betting it will still be well short.

So, I've tried to rewrite the story, using my first draft as merely an outline.  This is where the real problem comes in.  This story is locked in my head as is.  Any time I try and do this, I get nowhere, because the story is what it is.  So, I intend to try and do the cleanup I mentioned, but then what?  Publish it as a cheaper novella?  Toss it aside and keep attempting future rewrites that may never come?  I'm just not sure where to go from here.  And so, the story continues to sit...waiting...