I finished the game and had skipped some side missions and realized that I didn't get the trophies for finding all of the collectibles. Gun Collector for weapon parts, Armorer for circuits, Librarian for logs, Professor for artifacts. Were some of them in the optional side missions?
After going through some walkthrough videos on IGN, it is apparent that not only are some of the collectibles in the side missions, they are also in the CO-OP side missions. So if you're like me, playing solo, you have no chance at these trophies. What were they thinking?