This blue-bladed lightsaber was a weapon that had once belonged to Jedi Master Sifo-Dyas, who also owned another blue-bladed lightsaber during his lifetime. Sifo-Dyas carried the lightsaber at the time of his death, and it was abandoned on the desert moon of Oba Diah where it was discovered by Master Plo Koon.
Sifo-Dyas carried this lightsaber when he was called upon by Supreme Chancellor Valorum to secretly negotiate with the Pyke Syndicate. His shuttle was shot down over the desert moon of Oba Diah as a result of the machinations of Darth Sidious and Count Dooku. The Pykes delivered the Jedi Master's body to Dooku, but left the lightsaber in the wrecked shuttle.
Near the end of the Clone Wars, Sifo-Dyas's crashed shuttle somehow sent a distress signal that reached the Jedi Order. Master Plo Koon and troopers of the 104th Battalion of the Republic Army traveled to the Oba Diah moon to investigate, and discovered Sifo-Dyas's lightsaber in the wreckage. As the body was missing and Jedi records mentioned that Sifo-Dyas's shuttle had been lost on Felucia, not Oba-Diah, the Jedi Council began investigating the case.