[Anthony]

Since see secrets only detects things that were deliberately hidden, I assume that this implies that the act of willfully hiding something marks the object in some way. Therefore, something that is 'hidden' by an agent that lacks will (such as a golem, zombie, or machine) will not be detected, and the remove aura spell will erase the mark (this is explicit in the case of see secrets). In addition, protections on the hider at the time the item was hidden apply to later detection. However, later use by someone aware of the secret may reveal it.

In general, I make a rule that any spell that requires knowing the purpose or history of an object functions based on marks on its aura created by those using it who were aware of that purpose or history, and those marks are affected by mana level. This makes spells such as Recipe and Schematic quite marginal on objects manufactured by machine or in low to no mana zones. Also, because I'm mean, remove aura isn't a contest, it just causes the spell to fail.