:') Not that I buy it either, but the Norse contact has been known for over a century, but it wasn't until 1966 that remains of a Norse settlement in N America were found (that were widely accepted that is).
While it is true that the remains of the settlement were only found fairly recently, there were other Norse artifacts found in N.A. long before that. Buttons in New England, pre-Columbian iron artifacts in N.E. America, butternuts way south of where they should be, etc. That was what led archaeologists to search for Norse settlements.
People just can't move around without leaving trash wherever they go. We can't go someplace new without picking something up. If we come across somebody who has something that we don't, and we have something that they don't, some sort of trade inevitably occurs. It always has.
The Norse hardly traded with the locals at all (and were only driving longboats), and yet stuff that they made has shown up hundreds of miles away from their settlements. The Chinese supposedly launched a trade expedition with 450' ships, with the specific purpose of establishing new trade routes. They left nothing in North or South America, and they brought nothing back with them.
All that way, with thousands of men, and they never even used the little boys room? ;-)