I just read an ad for an IR Light that is attached to a license plate frame, when turned on it completely washes out the readability of the plate. So, it may not be your camera, but those that are up to no good, have probably put this on their car....
I've often wondered why business only have cameras installed at ceiling heights, looking down at the top of someones head, instead of one's that are eye level. Cameras come in so many different sizes, that surely one could be hidden at a 6 ft level. Likewise I would think that a camera would have to be mounted way closer to the ground to get a really good look at a license plate. Just a thought.