I see one screw on the rotor has gone..
Nope, that is one of the greatest misunderstandings of Rolex.
Only one screw is EVER used.
Below the rotor there are 5 screw holes, when you wind the rotor onto the shaft only 1 screw hole will line up snugly, and that is the one the the retainer screw goes into.
Its a VERY smart idea, as you can not know exactly where the rotor will stip when screwed down onto shaft, but with 5 holes below, one ALWAYS lines up.
Nothing missing, two screws means a bodged repair.
Regards