Reading difficulty

[“If I remember,” Malcolm said, “I predicted fence integrity would fail.” Hammond sighed, and sat down heavily. “Damn it all,” he said, shaking his head. “It must surely not have escaped your notice that at heart what we are attempting here is an extremely simple idea. My colleagues and I determined, several years ago, that it was possible to clone the DNA of an extinct animal, and to grow it.]

question

What does the "not have escaped one's notice" mean? Can you rephrase it please?