I was sure there was a fuse too! I searched all of the fuse boxes, checked the manuals, scoured the web, and nothing. I retested the bad wire further up from the plug to make sure it was not something with the connection on the plug...nothing.
Then I saw single post this morning from 2010 saying there are undocumented fuse boxes labeled with things like "ARENS" and "NOT FOR STORAGE". I opened every cargo door and there it was - "NOT FOR STORAGE""
The post said there might be 4 screws to remove - luckily I only had clips. Inside were more fuses. They were labeled RTURN, LTURN, MARKER, BRAKE, and B/U. Nothing about trailer. Regardless, I started pulling fuses - Bingo! The one labeled "MARKER" was blown. Replaced it, checked the lights on the Jeep, and I am back in business. Problem solved!!
Hope this helps someone else in the future...if there are wires running into an unlabeled box...it might be an undocumented fuse box. Open it up and save yourself 20-30 hours and a lot of frustration!!