Sickness
From PinataIsland.info, the Viva Piñata wiki
Pinatas in the Xbox 360 game never die unless, destroyed by a shovel. However a pinata can get sick. Should your pinata get sick you can choose to ignore the pinatas ailment or you can try to cure it. Should a pinata get too sick to heal it will leave your garden and return to the wild. It will also discard any accessories you have put on it.
