Quantum physics says an information is never lost, it just transforms or scrambles into the space and if we are able to reverse the direction of everything and let them roll again we would be able to find the previous state of the information again or we can just reverse the time to get the information back again as the equations or laws of physics is time symmetric.
But here is the twist. Hawking said a black hole is such an object which never lets anything escape out of its horizon. Let me tell you first about Horizon of black hole. Horizon is that layer around the black hole beyond which nothing can escape out and will get pulled enormously into the singularity and crush into it. Susskind explained it(in an article in magazine Scientific American, April 1997) with a beautiful example. Imagine a downstream river going into a black hole. We know the fastest fish is ‘Light fish’. If the downstream is as fast as the Light fish at the edge of the waterfall then if the light fish crosses that point it won’t be able to know that the next moment it wouldn’t be able to recover out of the downstream but it would get pulled by the stream because the speed of the waterfall would exceed its highest speed and the light fish would never be able to overcome the downstream and get crushed into the bottom of the river. This is what happens at the horizon. Light is the fastest particle in the world. But when it reaches the horizon the pull of the black hole becomes so high that the light gets pulled in by it. So, this means beyond the horizon of the black hole nothing can escape out.
So now coming to the conclusion, if the information is sucked into the black hole then will it be lost forever? According to general theory of relativity and Hawking it should get destroyed but if it is so then it violates the quantum physics and the energy will not be conserved, which is the most important law of physics and It would mean that energy can be created or destroyed. So perhaps we should look at it again and try to find a solution. Physicists were totally puzzled by these contradicting phenomena of black hole.
But Lárus Thorlacius was the first one to see that this is not contradicting phenomena but it is complimentary. He said like every particle the black hole also has radioactive character. So anything that is being sucked into the black hole will radiate to the horizon. Actually a black hole can have as high as 10 billion degree temperature at its horizon or as small as 10-8 degree also due to the radiation. Therefore we can retrieve the data by reading out the temperature if we could. All this can happen because of the entropy of the black hole. According to Hawking a black hole can have entropy of 3.2×1064 per sq. centimeter. Although the physical system consisting all these bits of information have to be very dense and must have linear dimension of 10-20 times the size of proton we may say that both of the statements which were contradicting each other can be complimentary also.