During Bill Clinton's Serbian genocide program. The wreckage was shipped to Russia. Like alot of folks, I assumed it was a gift from him to his friends.
The radar they are talking about is Doppler radar. Old style radar worked by "bouncing" electromagnetic waves off of conductors(like an airplanes metal hull).
Doppler radar detects the difference in velocity of media. It does not require that a target be a good conductor in order that the target be detected.
You can't get more stealthy than thin air, and doppler weather radar is used all the time to map wind patterns and storm fronts by detecting the differences in the velocities of air masses.
I doubt I will sink any ships with that one, but we all should to know that most USAF stealth technology has been not-so-stealthy for quite a while.