Aang had seen koh that time as well, conveintly un-aware of how dangerous koh really was. Koh had taunted aang at the time, and he had sumbmited (his thoughts had only been on finding twi and la) un-knowingly letting koh explore his fears.
like losing katara...
The path took a sharp turn and aang totally lost his sense of direction. He shook his head and chuckled softly. Of all the weird places he had been (such as the back of a turtle the size of a small island) the spirit world had to be the weridest. After a while aang started to wonder what had happend to hai bi and all the other spirits that usaully roamed these forest. The forest still seemed deserted but aang could hear strange caws and yelps resounding through the tree's.