The key word is "If": there was no time, in any place I know of before the Industrial Era, when anybody who knew the techniques of working iron could not find enough iron to work. Or, for that matter, any other metal. Uruk, one of the first major cities, imported copper from hundreds of miles away, from settlements established just to extract copper ores and smelt them and send them off to the Big City by pack trains. Rome imported iron from modern Balkans (before they conquered them) and so on and on.
Lack of Resources is a strictly Game Mechanic with no basis in history or reality until Industrialization jacked up the requirements for quantities of raw materials to previously unimaginable heights. Before that, resource scarcity never really existed: if you needed it, someone was willing to bring it to you for a price, no matter how far they had to lead a train of pack animals or sail a ship: Neolithic trade routes already went across the Mediterranean from Sicily to the middle east or from the Caucasus across the Black Sea with obsidian, copper, and probably a mass of more perishable goods now unknown. If you could pay for it, someone was willing to chance it.