I'm curious what you think "evidence that it never happened" would look like, except for looking like the absence of evidence?
What would evidence that there was never a global flood look like? One example might be "lack of a global species disruption in the fossil layer". But that's just absence of evidence again.
You're talking about the idea of the Genesis flood, occurring some 4500 years ago, drastically rearranging the recently-created Earth's geology, wiping out every living thing except for the few that survived on a boat that landed on a single mountain in what is modern-day Turkey?
I think there are some predictions you could make there. However every single one of them is just so far divorced from what we observe that they aren't even worth enumerating.
What would evidence that there was never a global flood look like? One example might be "lack of a global species disruption in the fossil layer". But that's just absence of evidence again.