Why on earth wouldn't a buff wouldn't be acceptable as a hat! If I carry an item that can only be used as a hat, it's usually one that's no thicker than a single layer of buff anyway, let alone in doubled-up form. And the hat has to be carried in addition to a waterproof jacket with a HOOD. Kit requirements for the skyline seem to be getting ever more ludicrous.
I have great sympathies for the good runner I spoke to during the week who decided not to do the skyline again when the requirement for a phone came in.