Why does the solution have to be simple?
The people of the Bronze Age were probably as complex as their convoluted trade/exchange systems.
If you have a technology based around skin boats and a beautiful Phoenician merchant ship, chock full of exotic people bearing exotic goods, sails into your fiord, is that not an event worthy of recording in your mythologies? Much as the people of the south Seas recorded the first European ships.
Dare I mention the Hyperboreans.