I’m looking for answers to this problem too. Add from server doesn’t help. While it does add files from the server to the library there are 2 big problems.
First the vast number of extra images wp makes for every image you’ve uploaded through the media library. It’s time consuming to pick through them all to find the original files.
But much worse is that it adds the image to the library but all the data you had entered in title, caption, description etc is gone. If you have a lot of images and have been using captions and descriptions in things like lightboxes etc, it means re-doing all your images from scratch!
Surely that kind of data is still in the database somewhere? Maybe it can be joined back up with the new image paths somehow?