Trade was happening long before Columbus sailed the ocean blue, and seeds might well have been swapped. But I find the story bogus not because the old seeds sprouted but because you say this artifact was apparently wrapped in a wet cloth. That's nuts--water is very destructive in the context of preservation of old stuff. I would be inclined to think it's made up for that reason. But more information regarding the origins of the bamboo and the context in which it was found might shed light on this story.

SRS