Driving & Driving Test Tips: radar guns, radar guns, radar units

I driving my mini-cooper behind my husband's pickup truck on a highway in PA.  He was about 100 yards ahead of me and both of us were in the left (fast# lane.  We were both travelling the same speed #which I thought was around 70 mph.)  I was pulled over by a state trooper who said I was doing 82 mph according to his radar gun.  I got a whooping speeding ticket, but no points.  How is it possible that the radar gun did not detect my husband, but it did detect me?  Also, nowhere on the citation does it record my speed or even that a radar gun was employed.  Under the "Remarks" section, the officer simply wrote "Mini"  (like that explained everything.)  How do those radar units work?

I suppose there could be several answers.

The first thought I had was that he did not have his radar set - I realize you were right behind your husband, but it may only take a second or two for something to distract the trooper- could be something came over his police radio.

Other reasons - maybe he was just clocking every 10th car.  

Its hard to say, unless you are sitting in the vehicle with the trooper.