It's always a personal shock for a law abiding citizens to run afoul the law when they meant no harm. Here is WA you cannot go under 35 MPH on a highway (unless a marked farm vehicle). You would get a ticket for doing that on a freeway due to creating unsafe driving conditions. i. e. Turbulence in the traffic flow. Too fast or too slow forcing other drivers to maneuver around you. I know you were all alone, but that cop you didn't notice thought it erratic. Anything outside the norm will get you noticed and at least talked to, often cited.