Some in Westford, Massachusetts, believe that an expedition led by Scottish Prince Henry Sinclair visited their town in 1398. Their evidence? A stone on Depot Street that bears the image of a broken sword—supposed to signify that a knight in the party had died.
So is this the stuff of legend or of history? Some people in Westford are hoping science can help them find out. They've contacted a forensic geologist about testing to determine the age of the carvings.
"So we just hope they can date it and that will convince the non-believers that the knight actually did come here in 1400," said [Elizabeth] Lane. [Link]

This is not a whole lot of evidence, folks. Speaking as someone who just realized she made a huge error in identifying someone with the same name, same age, same weird middle initial, from the same part of the same county - as her ancestor. And he wasn't. Maybe he was a cousin though.
Anyway, I think they have a little less potential evidence!
You're right, it might have been Henry Sinclair's cousin who visited in 1398.