There are irreversible logic gates, are there not? Gates who's outputs don't preserve information about their inputs, no? Or take for example computer parts that crunch numbers. If you know the answer to a calculation is 12 but that's all you know, then you can't figure out whether the calculation was 5+7, or 10+2, or 6x2, or 98,425-98,413, or the square root of 144, etc. So how can there be a conservation law with regard to information?