Amateur musician doesn't recognize legend

This didn't happen to me, but was a story told to me by an Uber driver when I asked if they had ever had any celebrities as a passenger:

The driver picked up a passenger at JFK airport with a destination on the Upper West Side of Manhattan. They're making chit-chat during the ride and the driver mentions that he's a singer/song-writer trying to get a break. The passenger offers some general advice and asks if the driver can play him a sample of his stuff. Driver plays one of his songs, and the passenger offers some feedback about how he thinks it can be improved.

The driver asks the passenger, "Oh, are you in the business?"

Passenger replies, "I dabble."

Two weeks later the driver sees a picture of the passenger on social media - It was Stephen Sondheim.