newbie with question

[Pale Rider]

If there is a link to this question then you can send me there- did do search but could not find exact answer.

First- I am total newb to radar detector.

I bought the Escort 8500 x50 and took a 16 round trip to DC.

I passed 10 different cop cars along the side of the road. My detector, before, during, or after never went off. I have it set to auto.

I have tested it and it works so I am sure it is not the detector.

In one instance I pass the cop and I saw him get out and motion a car three lengths behind me over.

So the question is what is going on. Given the fact my detector works, what are some of the explanations for this?
Thanks.

[GCH]

Easy... the cops never had their radar on.

[ELVATO]

The fact that he motioned a car over may suggest that they were using laser. Laser is very rarely detected if the car in front of you is shot. Even if you are shot, there is a chance your X50 might not go off, especially if the LEO knows how to use it. If there were alot of LEOs in a line, VASCAR might have also been used.
Basically, laser usually never offers advanced warning, while with radar, there should be some sort of advanced warning(especially with the X50) since they are two different types of technologies..

And, as GCH said, they might have turned off their radar when making their traffic stops.