I'm referring to what is clearly 2 conductor, black and white in picture below from the passenger dash side panel. I doubt it has anything to do with USB. Possibly proximity sensor for the doors? Take a look:
Where did you tap your power from?
Oh, that! That's the antenna/sensor for the key fob. Make sure you plug it back in!
On the other side in the passenger footwell area, if you remove the two pieces of plastic trim where the yacht floor is (or would be).. behind the second plastic panel are the cables that run to the USB jacks, including 12v power. I tapped into those for both
+ and -. If you don't see the wires right away, they're there, just hidden a little bit. I used vampire wire taps.