Hello,

has anyone seen this type of wire plug before? Usually the flat four is standard but this hitch only has two.

 

I have never seen a 2-wire plug for trailer lights though I do know they exist.
It could also be a connector for trailer brakes or cameras.

 

I would check it with a volt ohm meter. What that might be is a charging line. You have a class III receiver on your car. I've got one too even though I don't tow very often my my Mazda. However, what I do use it for is a bike carrier and sometimes an extra cargo carrier.

If I were to need a power chair, that carrier could go in the receiver too and the line may be a charging line to keep the chair charged. Check to see if either line has 12 volts. It may only be charged when the vehicle is running. Ground your meter to the chassis. I'll bet the white wire is hot and the black is ground.