The coins Kai got with the exploration would sell for good money. He also had the flute the goblin had used, but he didn't want to sell it. That item could be useful, and because Kai didn't know what it was capable of, he could not ask for the right price.
Once he returned to the city, Kai went to the adventurer's guild to speak with the attendant. The procedure was necessary after the completion of a task. This way, the guild would know and take out the task from their 'system.'
"Did you find the cat? That's great news," the attendant said with a smile. "I'll write it down your achievements. This counts as one mission completion for your resume."
The more quests Kai completed, the more his rank would grow, and eventually he would rise from his bronze rank and reach greater realms.
Of course, that would take a while. He didn't have the strength to be in the higher levels. He was still an Acolyte, after all.