Well the mouse was never invented! It was only honoured. As a matter of fact when humans were evolving the mouse was actually human’s best friend. In fact the mice then were not the same size as we see them today. They were larger, but during the course of evolution they grew smaller to hide from humans. Well that’s a different story altogether. So during the prehistoric days humans went out hunting with their pet mouse, who helped them with their unique gift of finding prey especially if they were hidden, and the humans in return supplied their pet mice with rich and cooked food.
This went on for a few years till the time the dogs evolved; well now you see that dogs had a special way to find things, they used their nose is never nibbled on their food, they also barked, to sent the intruders away unlike the meeky mouse. So slowly they replaced the mouse as human’s pet animal and till date it remains so (you know why the mouse shrank in size, to get away from humans and their greedy minds)
So well now coming back to how the computer mouse came into picture. When the computer was being invented they needed a pointer, something which would point out on the screen. And we know how the mouse has been great in doing this over the years, so own ancestors decided to honour their ancestors ex best friend who helped them search and pointed out it things. But alas the created of the computer had never seen the big old mouse which his ancestors knew of. So the mouse which we see today is smaller.
And hence the mouse was honoured and not discovered!