Someone would have found the data.

Are you arguing for young Earth creationism now?

Or is it an accident you're using their exact same logic?

Because to quote Donald Rumsfeld:

The absence of evidence is not the evidence of absence

Especially when what we're talking about is evidence of agriculture over 20k years ago, what the actual fuck do you think would still be there? A rusted out Ford tractor?

There's gonna be the same amount of evidence as for when I farted in 5th grade science class decades ago, that doesn't mean it didn't happen. It just means no evidence survived this long.