previous renter left radar detector in the car at IAD. Isn't that illegal in VA?

I picked up a rental from Hertz this morning. The car was super clean with just 1100 miles. I drove to the Embassy Suites in MD and was in the process of getting my bags out when I noticed a Uniden radar detector on the top center of the windshield, just behind the rearview mirror. It was installed with a suction mount. The power cord was nowhere in the car. I didn't have time to think about it until now because I had a meeting.

Now that I'm back in my hotel room, I started wondering..... a few quick questions:

(1) did the Hertz people not do a good job cleaning a returned car if they missed something as big as a radar detector? then again, it was behind the mirror, so even I didn't notice it until I was getting stuff out from the passenger side :)

(2) AFAIK, radar detectors are highly illegal in the state of Virginia.(where IAD airport is located)

(3) should I keep the radar detector? or should I give it to the Hertz guy when I return the car on Sunday? :)

Just in case the renter who left the detector actually reads this forum.... tell me what the make/model/color of the car for verification and I'll be happy to drop it in the mail for you. :)

Edi: just looked it up.. holy cow, when did radar detector become so expensive? this model is $699 on Amazon right now!!! (have not used a radar detector in over 20 years)