A lot of writers leave parts of a first draft in sketch form to come back and work on later, when they are in the mood or have done a bit more research.
There is a lovely bit from Louise Doughty's column in the Daily Telegraph, where she describes sending her finished manuscript off to her Agent, only to be phoned up later and asked about the gap in Chapter 10 where she had scrawled: "big argument scene here" - a scene she had not wanted to write, although it had to be in there, and so had skipped it in all the redrafts.

only to be phoned up later and asked about the gap in Chapter 10 where she had scrawled: "big argument scene here" - a scene she had not wanted to write

Yes, I've done that sometimes, or sort-of written it, almost like a skeleton without the flesh, or scrawled along side 'right idea but boring writing' or 'thicken this up'. Sometimes itsbecause I don't want to write it, sometimes because it's entirely dependent on some facts that I can't get hold of, sometimes because I know I'm not writing very well today, but it's still better to go on than give up.

Emma

Perhaps she reworked it as a little tiff

Emma

Hi there

Sagging in the middle

I am new to this. I have two books on the go at the moment (am I dreaming when I say that) I tend to have the same charactures but treat each chapter as a different story.
This seems to move things along towards where I envisage the end will be.
Thats hopeful.
I've six stories that link together for one book approx 30,000 words at the moment, still ongoing. The other book is coincidences in crime that link charactures together moving it along.
However you see it these things seem to have a life of thier own.
Hope you find the right path
All the best
Joe.

I agree with Emma that my first drafts are like very detailed plans, but I don't realise that until after I've written them! I always think I'm writing the final version... till I re-read it six months later and go 'oh...'

There was an interesting article in last Saturday's The Times Books section about the number of crime writers who do not meticulously plot their books, but write as though they are driving at night and can only see as far as the headlights can reach. It is not until they get to the end of the first draft that they have their basic structure. Then it's just a matter of adding some layers and flesh out the rest. They also recommend cutting out the first and last chapters, because they give away far too much to the reader

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http://entertainment.timesonline.co.uk/tol/arts_and_entertainment/books/crime/article2549858.ece