Thank you for fixing my bike chain with a stick

My bicycle chain jumped off on the BeltLine Eastside Trail in Old Fourth Ward one Sunday morning and my hands were black in seconds. A man jogging past stopped, flipped my bike upside down, put the chain back on with a stick, and wiped his hands on his own shirt. He said, no worries, I have done that fifty times. I rode the rest with a very clean conscience and a very dirty sleeve. I would like to buy him a shirt. I would like to know his size.