Digimon World: Dawn and Dusk/Find Tapirmon

When you've activated the quest, go to thriller ruins. Go up the first ladder for an item. Go back down and take the upper path to the next map. In the next map search for a ladder, climb the ladder, and go to left to find another ladder. Climb it and you'll find a box with a thriller key in it. This is needed for later. Go down the ladder and go right and then up and you will find Tapirmon. Just talk to him and he'll send you back to the town to talk to the client.