
I've always appreciated the old fan theory that Luke's green lightsaber used the crystal from Qui-Gon's that Obi-Wan had saved, and he found it upon returning to Obi-Wan's hut on Tatooine.
Since Obi-Wan used Qui-Gon's lightsaber for a time after his death and likely had some attachment to it, it seems likely he would have held on to it and even made sure to grab it from the temple when he and Yoda returned there in ROTS, anticipating someone's need to build a new saber eventually. It seems like a good legacy to carry on.