You are right, absence of evidence is not evidence of absence. However extraordinary claims, require extraordinary evidence, and while there is no evidence of an ocean fairing civilization in the 16th century BCE I will believe the simpler explanation that the reason why American crops were cultivated in India is because seeds were brought by winds, currents, birds or insects, but not humans.

I guess I should have been more careful in may claim that “the technology did not exist”, and should have worded it as: “we have no evidence for such technology existing at that time in human history”.