Last January, my brother ran into one (literally)fishing a small OP river. He was wading downstream about to cross under a fallen tree that was about head level when a cougar jumped onto the log above him and hissed at him. He fell back in to the river (over his waders) and he saw a baby cougar on the bank. His fishing partner was just across the river and started yelling at the cougar and luckily they both ran off into the woods. He said if he hadn't fallen into the water, it looked to be ready to jump on him.

I myself saw cougar tracks on 3 consecutive trips to the Hoh/Bogie/Sol Duc last winter also. All alongside the riverbanks. They are definitely out there in numbers on the OP.