What an ETM is is the electrical diagrams for the car. ETM is the abbreviation for Elrctrical Troubleshooting Manual. Typically, you find it on a shelf at your dealership, I don't know why he thought you would have a set of ETM's for your car.
I would continue a "good light" search for the socket. If you have a continuity tester (test light) you can possibly connect it to these 2 wires and turn on the parking lights to see if there is in fact power and ground present at these 2 wires with the switch on. Keep looking for the socket, remember it can't hardly be farther away than the wires will reach.