Any angle other than straight on with radar will display a slower speed, never higher.Most likely by the time he was able to get a radar lock on your bike he was so close to you that he did not get a straight shot at you oncoming but instead it was from more of an angle which will give a false reading on speed (usually higher)
Radar measures how fast you are approaching the unit sending the signal. Any time you are not traveling directly at the unit, it reads slower because you are not approaching the unit as quickly as you are moving.
One other comment...I wouldn't be too keen on getting frisked for just speeding. WTF is up with that? The cop is nervous? Too fricken bad, he should get another job, not violate anyone's rights without due cause...
Blue1