The phrase “lost on an island” suggests (at least to me) the image of a relatively small and isolated island somewhere in the tropics, with a very small population and no modern technology – an image reinforced by the reference to the island having a local witch doctor. Let’s say, something along the lines of Skull Island in King Kong. What I’m having trouble understanding is: why would there be a second-year medical student on such an island? Did he get shipwrecked too (which is how I’m assuming that I got lost on the island in the first place)?
On the other hand, if we’re talking about a large island the size of, let’s say, Java, with a population of 143 million people, and that I’m lost on it simply because the GPS on my rented car broke down, and that there are enough witch doctors and second-year medical students among its inhabitants to make it plausible that I’d run into both types of persons simultaneously, my guess is that this would only be likely to occur close enough to a developed area that I’d simply choose to ask these fellows for directions to the nearest medical clinic or hospital.