Access to First Class lounge is restricted to OW Emerald and First Class passengers only: http://www.oneworld.com/ow/ffp/loung...search#Lounges

However, in Santiago you should have had access to the Pablo Neruda business class lounge based on your class of travel and/or OW elite status:

Business class lounge access entitlements: http://plane.lan.com/info_viajes/en_...vip-en-us.html

OW Sapphire entitlements:
http://www.oneworld.com/ow/ffp/loung...search#Lounges