Happened to me, took like 5 ingame minute for kerfur to respawn by the main transformer. Not sure if there is anything you can do to make it go by faster but it just dropped kerfur there randomly. Maybe its random everytime?
it's been a few days and i haven't found any sign of him, i've heard he has a range that he could come back from but i'm not sure how much of a range it is
