I was changing mast/decklight for SAFA and I was not 100 % careful .... and the old cable dropped into the mast ... so I don´t know the anatomy of Nautor mast (original), are the electronic wires in their own pipe/hose or freely hanging in the mast? And recomendations and instructions to catch the cable ...
All cables run in a PVC tube attached to the inside along the mast forward edge. The success with this task depends very much on how many cables there are in the tube. Fewer cables make the job easier. There may be two tubes if there are many cables.
Pull out the lost cable from the mast lower end, and try to thread in a nylon cable puller into the cable tube at the light level. If this is successful the lost cable can be connected to the puller and pulled back in.
If the cable puller refuses to go in from above, fish out another cable from the cable tube at the light level, disconnect it at the lower end, and use it to pull in two cable pullers from the lower end. Now you can pull in the lost cable, and pull the disconnected cable back down.