The problem is often that those outpost were only for mercantile purposes and left not much behind. There has been some European metal artifacts found deep into NA and indicate prior contact / pillaging of those outposts. We have Vikings archives from Greenland that survived to this day, but not the other outposts. Evidences tend to show Vikings sailed far into Labrador, Baffin and the St-Lawrence river, but never did much and Inuits took everything they left behind. Basques were interested in fishes and whales, not settlements and again left nothing.
If we exclude prehistory, there is only a 130 years "gap" between known European activities in the "New World". Vikings/Normans came well into the 14th century and Basques (from ports close to Nor[se]-man-dy) came in the early 16th century.
If you include Cabot in the late 15th century. IMHO that looks like a rather small gap to "rediscover" things. At that point I wonder if it's harder to prove that the knowledge was fully lost or prove that it wasn't.
If we exclude prehistory, there is only a 130 years "gap" between known European activities in the "New World". Vikings/Normans came well into the 14th century and Basques (from ports close to Nor[se]-man-dy) came in the early 16th century.
If you include Cabot in the late 15th century. IMHO that looks like a rather small gap to "rediscover" things. At that point I wonder if it's harder to prove that the knowledge was fully lost or prove that it wasn't.