I had a problem a few years ago where my cable froze and would not retract the flap all the way. I ended up replacing both cables but I don't believe they are available any longer. This is the part number 05140962AA. As Pizzaguy stated, both sides are the same, so you should be able to look at the one that is working to see how it is attached to the flap or the hydraulic cylinder. I'm not sure how it could just fall off as there are torx screws that hold the cable receiver to the flap. the cable is attached to the tonneau cover hinge with two zip ties and then runs to the hydraulic cylinder. if you take the trunk fender liner out you will see the cable and how it connects to the cylinder. Hopefully the link Pizzaguy provided to the top manual section will help.