LIMA (Reuters) - Thieves who stole a $100,000 ceremonial garment from a Peruvian museum by covering up the crime with a chicken feather substitute left the cloak in a nearby church confessional box on Tuesday. Curators said they did not know how the pre-Columbian cloak - made from more than 560 parrot feathers and dating to between 700 and 1200 - was stolen last week from the municipal museum in the southern city of Arequipa. Nor did the officials, informed of the cloak`s whereabouts by an anonymous phone call, know who placed it in the confessional. The theft was discovered last week after museum officials noticed the six-foot (1.8-metres) cloak`s blue and yellow plumage had lost its usual shine. Tests showed a modern chicken-feather cloak was standing in for the pre-Incan treasure. The cloak, valued at $100,000, was one of 40 ancient artifacts discovered in 1943 in Condesuyos province around Arequipa.