If you don't see the cable at all, it was cut/broken like you said, and probably retracted into the module itself......I don't believe you can just get the cable to replace it....it involves buying the whole module, which is very expensive...
They do sell models, where the right side is motorized, and the left side is manual.....I would treat your vehicle the same way......the cost is prohibitive to fix......
However, if you are mechanically inclined, and determined to fix it, you should get a manual, so you will know what you are doing.....and you can check local boneyards, to see if there are any available.....problem is, most charge close to what a new one costs, and it's possible, it may not work when you put it in(defective).....