The ghosts keep trying to scare Louis ever since he lost his courage medal. He asks Mickey to go find the medal so that the ghosts won't be able to scare him anymore. The courage medal can be found inside the Sunken Steamer boat close to the Projector Screen where you enter Bog Easy.
Once you find the medal, you can return it to Louis. Louis will thank you for finding his medal, and will let you heal yourself at his shack anytime from then on. This path automatically fails the quest Help Gilbert Scare Someone.
Gilbert offers to buy the medal off of you for 200 E-Tickets, because if Louis gets it back, he won't be able to scare him. If you give the medal to Gilbert, Louis will lose his courage and this quest will be a failure.