It is in the plaguelands, your beat bet is to move back and forh between the area out from of the archon's forge, and the area with the high kedge that has the ship containers up top. Sorry I forget the area names. Its a random chance among the other patrols, so if you just keep doing patrols eventually it will pop up. My friend says its quicker to sparrow through and if you don't see one, go to orbit and repeat.