[Heiko]

Sometimes they tuck the release cable between the rear bumper skirt and the heat shield on the driver side... if not you'll have to pull the
skirt on the driver side (one screw at the top of the skirt (torx) inside the wheel well and another of the same size underneath and pull the
two smaller ones at the bottom of the rear bumper skirt as well (those are likely phillips heads).
Then gently pull out on the lower edge (bottom of the wheel well) so you can see up in behind... you should be able to find the cable :-)
Best of luck If the loop is rusted or broken off you'll have to grab the wire with a pair of pliers and give it a good tug... best of luck .
H