De acordo com Wookiepedia :
Following the Declaration of a New Order, clone troopers recovered Grievous's body, transporting it and his captured starfighter to one of Emperor Palpatine's secret storehouses on Utapau. There it would remain to collect dust for years, until the cyberneticist Nycolai Kinesworthy used the body of the general for the N-K Project, to create the highly advanced droid N-K Necrosis.
This war droid enjoyed a brief life in the Myyydril Caverns on Kashyyyk, before being destroyed by an anonymous group of spacers. The combatants looted the droid's remains, taking its weaponry and anything else they deemed valuable (source: "Star Wars Galaxies" MMORPG game)