Still looking for the man who paid my ferry fare at Puerto Juarez

I had the wrong amount in my pocket at the ferry window in Puerto Juarez one Saturday morning, and a line was building behind me. A man in a work shirt leaned over, put the missing coins on the counter, and walked straight to the boat without looking back. I have been trying to find a way to return it for months. Cancun is big. I stand on that dock at ten every Saturday with the exact amount in an envelope. The envelope says, you. I do not know his name.