Where's the Trailer Tow Prep Wiring

Trying to figure out where the factory installed trailer wiring is. Going to put a Class II hitch on my SES and trying to figure out if a 4 wire cable and plug are available. And where they are hidden in the car. There are "access panels" in the cargo area, but I've yet to investigate them. Quick look underneath was not productive, and my Ford Dealer's parts department was clueless - tho they did say they will be researching the issue.
There's an RV outfit in Manassas VA that ordered it for me. Two options the Curt and the Draw Tite - Both Class II. Now to dig out the factory wiring...
Thanks Mike,

I've been under the back several times and can't seem to find anything coiled up or anything that's readily visible. I had a thought that I might need to take off some of the panels under the bumper to see if it's coiled up there or something. I'm trying to get this info prior to pulling the trigger on the hitch.
Thanks again.