So... What if I had let korg go and how do I encounter him again :(
if your talking about freeing him from the cell you had to wait for him at the cave entrance.
If you used the love potion on him, then he got angry at you for doing simliar what the sucubus did to him an left an wont ever repear.
If you did either of these you have to go back to a previous save or start over