I heard four slow bars on a trumpet in the snow and never found the song

It was snowing sideways in Millennium Park at 9pm, and nobody was around except me, a man with a trumpet case, and a very large silver bean. He opened the case, tapped the valve twice, and played four slow bars that made the snow look like it was following the tune. Then he packed up and walked toward the L. I stood another five minutes. Best concert I have ever been to alone. I have not found the song. I have not looked. I think it was written for one evening.