Some historical events can come and go and not leave a trace of evidence.
As do
all not-at-all-historical, completely-made-up-events.
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But I don't see why you bring up this line of argument. Is it your contention that the Flood is the sort of event that would leave no evidence? If we were discussing (for example) the talking snake, you might have a point --- what are we meant to find, fossilized snake words? But in the case of the Flood, surely it would have left some trace?
Edited by Dr Adequate, : No reason given.