It sounds like a speed camera. Mobile one can operate out of holes cut into the back of vans or be mounted on small tripods (about 2 feet high).They do not need an operator with them, he is usually undercover a little way off the road. Surveyors equipment does not flash! The fact that you have been caught does not mean you will be prosecuted- sometimes they are used as a deterrent, sometimes you are so little above the speed limit they don't bother (10% used to be the rule), sometimes they just can't be bothered. I would have thought you would have heard within a week.