The unit I was in was responsible for our short-range air defense kit (Rapier FSC) tracking the B2 at RIAT at Fairford. The excrement really hit the fan when BAe gave the tape to the news. The USAF spokesman said it wasn't in 'stealth mode'. We just wet ourselves when we heard that.
The truth is that it was tootling along a few hundred feet above the centreline of the runway, well below it's normal mission altitude. We couldn't use the radar as the system was too close to the runway (for some reason pilots don't like radars inadvertantly detonating the det cord used to break up the canopies when they eject), so we used a bit of kit called a pointing stick. It is literally what it says, a stick with a trigger, press the trigger and it slaves the trackers to it. We then used thermal auto tracking to follow the B2. Whatever you do you can't hide the skin temperature of a flying aircraft. Both sides cheated, but their excuse was laughable.
This reminds of a story (no doubt embroidered), about Concords being used to simulate Russian bombers in NATO exercises. The concord pilots were mostly ex-RAF and did not serenely fly into USAF arms. In the version I heard transiently switching off the transponder and the fact that delta winged aircraft are naturally fairly stealthy meant that the USAF failed to intercept any concord on a bombing mission. (Also the concord could fly higher and faster than any US interceptor.)
I am sure posters here know far more than I do, so I am happy to be told this is nonsense. Just do it nicely!