As far as I know, Hanham isn't even on the cycle path. The closest it passes is Oldland/Bitton, which is at least a mile and a half from Hanham.

-It'd be helpful if the report was a bit more specific.
I remember a couple of years ago cycling back one night (-probably 9 or 10 ish) from an Urban meet up in Bath. Once I got beyond the edge of the city, the vast majority of the path was pretty much unlit, so for miles at a time I was cycling in almost total darkness.
A few times, there'd just be random people walking along the path in the dark, and you couldn't see them until you were a few metres away. Even with bike lights and the occasional overhead street lamp, once you got to those bits near Bitton, Saltford, Warmley, etc, there were long stretches where you couldn't see who's ahead, behind, or (-more likely in the case of this latest incident) who's to the side of the path.
Basically, it's easy pickings for would-be muggers.