Unable to find a user-defined type in an c++ unordered set with custom operator==()

Problem Statement: Iterate over an array of objects and check if the object exists in an unordered_set.

Goal: I could have thousand of objects in one container to check their existence in millions of objects in another container. I choose unordered_set for its constant finding complexity and vector for iterating. I'm new to this and if you have any alternate approach, I'd really appreciate it.

Issue: unordered_set find isn't working as expected or I got the concept wrong!

Main:

int main() {
  std::vector<std::unique_ptr<Block>> vertices;

  vertices.push_back(std::make_unique<Block>("mod1", "work"));
  vertices.push_back(std::make_unique<Block>("mod2", "work"));
  vertices.push_back(std::make_unique<Block>("mod3", "work"));

  std::unordered_set<std::unique_ptr<Block>> undefs;

  undefs.insert(std::make_unique<Block>("mod1", "work"));
  undefs.insert(std::make_unique<Block>("mod2", "work"));

  for(auto& vertex : vertices) {
    auto search = undefs.find(vertex);
    if(search != undefs.end()){
      std::cout << "Block: " << vertex->getName() << "\n";
    }
  }
}

Block Class Overload:

bool Block::operator==(std::unique_ptr<Block>& block) const {
  return block->getName() == mName;
}

Expected Output:

mod1

mod2

Block:

#pragma once

#include <string>
#include <memory>

using std::string;

class Block {
  private:
    string mName;
    string mLib;
  public:
    Block(string const& name, string const& lib);
    string getName() const;
    string getLib() const;
    bool operator==(std::unique_ptr<Block>& block) const;
};