oh! I read your comnent wrong, my bad.. I thought you wanted the bandits (and Gunnar) to show up but that didn't happen..
I don't remember how high the stats were in the beginning but I made sure thst indeed Appearance was one the higher ones when I started and I already run into Gunnar couple of times...
You can also run into Gunnar when the caravan is attacked but decide to submit to the bandits instead of fighting them off.