If it is the mission on PJem, iirc, from the monastery, you simply head down the the path to the bottom and then get a prompt to scan for him. Fight and defeat him. Then he will flee to his ship (beam out).
Get to the top of the monestary (where you discover he is a shape shifter)
Fight you way down the path (different than the path you came up on).
Should get a prompt to 'scan' for him at the very bottom