Why does std::unique_lock still point to a given mutex even after calling unlock?

As you can see in below code, I have used a unique_lock to lock the mutex mtx1. So because of that, lock1 is pointing to mtx1. After that, I have unlocked mtx1. Then I checked again whether lock1 is still pointing to mtx1 or not. I found that it is still pointing to mtx1.

Why is lock1 still pointing to mtx1 even after I unlocked mtx1?

#include <mutex>
#include <thread>
#include <iostream>
#include <thread>

std::mutex mtx1;

void task1()
{
    std::cout << "In start of task1 " << std::endl;
    std::unique_lock<std::mutex> lock1(mtx1);
    if(lock1.mutex() == &mtx1)
    {
        std::cout << "I have locked the mutex mtx1 " << std::endl;
    }
    else
    {
        std::cout << "I have not locked the mutex mtx1 " << std::endl;
    }

    lock1.unlock(); //used for unlocking 

    if(lock1.mutex() == &mtx1)
    {
        std::cout << "I have locked the mutex mtx1 " << std::endl;
    }
    else
    {
        std::cout << "I have not locked the mutex mtx1 " << std::endl;
    }
}

int main()
{
    std::thread t1(task1);
    t1.join();
}

output:

In start of task1 
I have locked the mutex mtx1 
I have locked the mutex mtx1