Blacksheep,
This is where the problem lies...
A credible witness reports that he noticed the flaps remained stowed during the approach. This confirms that option a) is the case.
Yet, there are also credible witness reports at the airport who saw the plane went by them stating that the flaps were deployed for landing (they are familiar with seeing flap30/40 for 737 landings).
But the purpose of the question was not to say whether that was deployed or not, but to propose 2 alternatives based on one or the other.
From the photos, they do appear to have ended up with a flap15 position or thereabouts.
Thanks for that...
PK-KAR