We can't say that such an increase has not happened, you are correct, since the resolution of the historical data is not the same as the present. But I think it's highly unlikely to have happened before.
My main point being that it took millions of years in a very slow process to sequester all of that carbon into the Earth. I can't imagine any natural process that would be so methodical as to extract only the pockets of carbon in the ground and put them back into the atmosphere. Even an asteroid impact would only dislodge and release a small section of carbon around the impact. There are no natural processes that can release all buried carbon on a global scale within a span of 300 years (assuming we pump every last drop out of the ground in the next hundred years).