Let's say they claim that they did find classified documents.

The People then ask, "what are the classified documents you allege Trump shouldn't have kept?"

And they'll say

That's classified information.

Following that logic, they can raid Trump for documents that actually don't even exist simply by hiding behind the veil of classification.

Even documents that seem benign, like a dinner invitation list, could retroactively be deemed of a classified matter and there is no agency or power whatsoever that can hold them accountable or question the authenticity of the classification in any reasonable timeframe to prevent the raid.

They could literally claim that a tissue paper Trump had in his keeping was involved in a top secret operation as evidence, sign off on the warrant, shove it in a sealed vanilla envelope, and use that to do whatever the hell they please. When asked why they are raiding a former President they can whip out the envelope and when asked what's in it that gives them the right to toss your crap, they pull it back and say "that's classified information."

This is how the scam works. This is how bureaucracy works.

You can't prove your innocence because you first have to prove your innocence in order to get access to the evidence that proves you are innocent.

You can't purchase a gun until you prove you can responsibly own a gun and you can't responsibly own a gun without first having purchased a gun.

You can't take out a loan for a house until you prove you can pay back your loans, but you can't pay back a loan if they won't loan you the money.

This is the peak of Government Tyranny; to make rules which actively prevent you from following the rules.

Giving people the roundabout when they try to exercise their God-given Rights...

And when you question any of it, asking what evidence they have of your guilt, you get the same response every time:

"That's classified information."