I don't have any specific stories, but my local rescue team in Cape Town now uses a drone on many mountain rescue callouts to assist in locating the patients.
It is surprisingly difficult to use a drone effectively for that - it is much harder to spot someone from a drone's camera than you'd expect. It is often still faster to find the patients by foot, but it has helped in some cases. And when the patients have been found, the drone can help to scout the surrounding area to find the best route out.
So overall the drone has been some help, but it hasn't significantly affected the outcome of rescue operations in any case that I know of.
It is surprisingly difficult to use a drone effectively for that - it is much harder to spot someone from a drone's camera than you'd expect. It is often still faster to find the patients by foot, but it has helped in some cases. And when the patients have been found, the drone can help to scout the surrounding area to find the best route out.
So overall the drone has been some help, but it hasn't significantly affected the outcome of rescue operations in any case that I know of.