Can he give me a ticket on my TLC license even though i wasnt working,? can he give me a ticket and not even mention it at all?

So I was parked momentarily right next to a sign that said no standing anytime, I was driving a TLC car because i am cab driver. However i was not working i was simply waiting for a friend to come out of a restaurant. Then an undercover cop or something came up behind me and banged on my window and asked for my license and registration, he also asked for my For- Hire license even though i stated that i was not working i was simply waiting for a friend. He takes my things and later comes back and says just make sure next time you dont park in a no standing zone, i said ok. About a week later i get a summons in the mail from the Taxi and limousine commission. The office never mentioned to me that i got a ticket at any point.