Series 3 Episode 7 "Honour Code"

Just before the end credits in Black and White Gibbs is seen sanding his boat with the boy Zach whos father he has rescued then the scene changes to him sanding a boat with his dead daughter. His daughter is wearing an NIS t-shirt but at the time of her death Gibbs was still in the USMC and had not yet joined NIS/NCIS.

However, Mike Franks was in NIS and he had probably given Kelly the shirt.