That story is from Ben Rich's book "Skunk Works". https://hipandthigh.wordpress.com/2013/03/18/blackbird/ describes it as "Lt. Colonel William Burk Jr., who shares about a particular mission he flew over Lebanon back in 82." That link also has the full account, ending "What he had given him was “the bird” with his middle finger" - that is, it was not sent by radio signals but by visual light to the Mark I eyeball of the Mirage pilot.