I just disfigured Campbell, but didn't get his journal (as far as I could tell). Normally I'd just reload, but my previous save is from before entering the main building. So what I want to know is if this matters at all, is there any effects on quests, rewards etc?

The journal was on his body so when you picked him up to carry him to the chair it would have been picked up. The game wont let you leave the area with Samuel without the journal anyways.