indian treasure is not a product, it is a quest item. it can still be put in the product slot however, since that product slot's purpose is not really the product slot, but as the product and quest item slot. it is referred to as the product slot because that was the purpose, before they started implementing the quest items.
also, never assume that something labelled a product can be found on a specific job. products exist that are actually found as random drops.
as for your indian treasure, look at the weststats adventurers quest line:
http://www.weststats.com/Questgroup/?group=28
it is in fact a quest item.