Today I was cleaning my engine bay, removing caked oil/dirt crap. I removed the grille so I could clean thoroughly around the radiator and found a disconnected cable that I can't figure out where it belongs. It comes from the drivers side and reaches as far as the centre of the grille (see pics). It is not from the fog light, neither the ambient temp sensor, I thought I could be the horn cable but as far as I can see it is connected and it works normally.

As far as I know it seems that it has been disconnected since I own the car (a little more than 2 years now), but haven't really noted any malfunction. The car is a 2004 coupe. Any help is appreciated.