First of all, anyone with a strong sense of smell would immediately realize that Olive was slightly reeked of smoke. Yes, the meals being served in the restaurants camouflaged it, but it still didn't escape him.
His sense of smell was higher than the rest, giving him the advantage of retaining the smell of anyone, even if it was just a few seconds or minutes of the meeting.
Last night, when Olive walked into the restaurant, he was able to tell that Olive was there due to the smell that he had retained. It was possible because they had met before, at the ceremony.
Now, not only did Olive smelt of smoke, but his white shirt was also smeared with ashy dirt, hinting at the fact that he had been in a place where something was burning. He was very sure that even Olive himself did not notice the ash, as even his hair was a bit colored by it.
