Not sure when this happened because it was back shortly after the game first came out, but Joeri Martens seems to have become permanently unavailable. I've beat the game and all the extra side missions, so I know it's not that. I'm basically just running around recruiting people and having fun. I've gone to all the spots on his deep profiler and he never spawns. I saw there a thread on this on the old forum, so I'm hoping they are working on it.