2002 Six Pac T150 Camper Prewired Speaker Locations...?

The Six Pac literature specifies an optional factory prewire for 4 speakers and it is definitely a speaker wire and not an antenna wire. I'm not sure if the 4th wire has retreated up into the ceiling or if the 4th speaker is intended to be mounted adjacent to the stereo. The wire matches the other two speaker wires (thin with clear insulation) and is not coax or power type of wire. It goes up into the ceiling hole and seems to go toward the center of the ceiling as I can hear it when I jiggle it. I can only trace it a few inches though. Sinc the existing two speakers are already adjacent to the stereo I would expect the other two to be on the other side of the camper. Normally, prewired items are indicated with a sticker or plug or something but I cannot find the slightest hint to help me. I have contacted the company but they no longer make campers and I'm not sure if I will hear anything back. Meanwhile I'm keeping my eyes out for a similar camper that has the speakers installed already. So far my internet searches and even the company catalog pics do not reveal the secret of where the wires are supposed to be prewired to.

Are you sure it's not the antenna? A third speaker wire doesn't make a lot of sense. Post a picture.