Hi Travs I always carry one of these :-
http://www.travelsage.co.uk/sawyer-m...system-review/
and for the couple of ounces it weighs I find it well worth while and have used it to get water from some pretty distasteful sources.
Whilst I don't doubt your account of the adventure you had, I have to say I am puzzled as to how you were unable to find water as personally I would have used the horrendous storm you describe to harvest water from
the run off from the Bivy to fill any containers I had to hand.
Also I assume you missed the obvious way down from Thornthwaite Beacon to Hartsop as the path runs from Threshtwaite mouth past Threshtwaite Cove and Raven Crag into Pasture bottom and follows Pasture Beck all the way to Hartsop.
Still the good thing is you made it and learned a lot
My next outing with the tent will be taking in all the 20 Wainwrights on the western side of Patterdale starting with Arnison Crag and finishing with Great Mell Fell, not sure yet when I will be setting off