Here is the problem with your claim.  If you run a tag and it came back as something you've never seen before it does not indicate an alarm of the tag. It indicates an alarm with the system being used. 

He said it came back with nothing he has seen before so obviously it didn't comeback as INVALID, STOLEN, GOOD or whatever.     It came back with something he has NEVER SEEN before.   So there really was NO REASON to pull her over because the system was obviously malfunctioning.   

So we are back to square one.    Why did he pull her over? 

Nothing was wrong with the window tin either.  A quick run from another car would reveal the truth. 

Nothing came back is a SYSTEM issue not a driver issue and definitely not an alarm that the car was suspect.   

Tired of people pointing to bad laws to lean on.   Obviously you don't remember this countries history with bad laws.  Keep it real.