That is correct: absence of evidence is not evidence of absence. The philosopher, Bertrand Russell wrote that if he claimed that a perfectly formed teapot were orbiting the sun in the asteroid belt, it would be nonsense for him to expect others not to doubt him just because they could not prove him wrong. Russell was illustrating that there was no evidence for the tepot, but reasonable people would conclude that it does not exist. His teapot is still referred to in discussions concerning the existence, or otherwise, of God.