It's shiny, the odds are very high that a human would indeed have seen it. For one thing, a human's eyes are constantly processing the world as they move through it. Curiosity's eyes are not.
What Curiosity has done in 6 months could have been done in a couple of weeks by a human, sleep time included. Robots are vastly inferior to humans for this work, and will remain so for some time to come.
What Curiosity has done in 6 months could have been done in a couple of weeks by a human, sleep time included. Robots are vastly inferior to humans for this work, and will remain so for some time to come.