My switch was located inside cargo bay on drivers side of the trailer. There is also a light in the cargo bay and it was right next to it. I would go and check mine but I'm in Newfoundland, Canada and my trailer is in Manitoba.
The trailer is similar but depending on the day they were built you may find the switch some where else. Check the cargo bay area and then check the switch panel inside the trailer and any other switch you see and see if they come on. Also, there may be a loose wire behind the light since you don't get two on at the same time. They should not be connected to your tow vehicle lighting system as when you turn your lights on and the clearance lights come on on the trailer. Clearance lights on the trailer are at the top on front and back and along the sides.
2014 Sunset Trail Reserve ST25RB
2013 Toyota Tundra Crewmax Platinum 5.7 Tow Package