And something else, he remembered Aiden saying he might go there himself someday. That day after they hunted, that's when the event took place...Ava wasn't with them anymore at that time.
If it happens to be that it was Aiden that went there, Oliver wouldn't be upset at all. What right does he have to be upset when he's gone to the river himself? When he was the one that told Aiden about the river. And when he was the one that showed Aiden the paths that led to the river.
But he wanted to know if it was Aiden or not, he was having a strong feeling it was him. Something else was running through his mind, why did he let himself get caught? And according to what he heard, Aiden was wearing a mask? That's why he easily let them sight him 'cause they wouldn't see his face.
He was gonna ask, Aiden, that's for sure...he hoped Aiden would tell him the truth.