there is simply no evidence. Since the Shawnee are part of the larger Algonquian linguistic/cultural group, there should be corroborating stories about arrival from the Pacific among other Algonquian tribes.
Regading Fort Ancient, in anthropological use, it is simply the name given to a pre Columbian culture who lived where Fort Ancient was later established.
Native Americans did have a very extensive trading system. They used rivers like highways. The Mississippi took Native traders as far south as the Gulf of Mexico. Tributaries of the Mississippi took them far in both the east and west for trade. In the area where I grew up in northwestern PA, it was possible for preColumbian people to get trade goods from as far away as the ancient Adena and Hopewell cultures of southern Ohio via the Ohio River to the three rivers conjunction where Pittsburgh is today, to the Alegheny River, and finally to French Creek, a large creek that extends out from the Allegheny. The Allegheny (just one of several different spellings) goes on into Seneca tribal territory in western NY.
So objects that originated in one place can turn up anywhere along a trade route without the tribe who received it ever having lived in the area of origin for the objects. The Maya had traders who sailed the coast of the Gulf of Mexico up to where New Orleans is today. From there, the people of the Mississippian Culture could (and did) in turn, trade some of those Mayan objects farther north for items from northern people. People on the Gulf coast also absorbed some cultural customs from traders to the south of them, which gradually spread northward along the Mississippi trade routes.
There are archaeological trails of trade that can be dated, showing that items were traded from a different group than the ones who received them.
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