It's underneath the headlight on the left hand side. The bracket my finger is pointing at.

 

With that square hole it likely is a spot for a wire loom clip to snap into. A lot of those have a square snap on them. I am trying to recall what runs across there from memory. My S2k is sitting on the trailer right now, but when I pull it into the garage I can look for comparison if you havent figured it out

 

Air pump stuff