I’m gonna go out a limb and suggest someone in a
carshaped
Object overshot the
blind sweeping bend
Call me Columbo.
Don’t know about Columbo…
From how OP describes it, it sounds like the ‘offending vehicle’ for want of a better term will be one of the two carshaped markings and perhaps the next vehicle following the cyclist is the other, (this 2nd vehicle wasx also struck by another cyclist) I don’t know what happened but having cycled and driven that road daily for donkeys years, i’d say it was more likely to have been the cyclist who overcooked it on his descent rather than the car.
As above tho, RIP