Oh, pee and poop issues...When you say locked away, where? Do you mean like in a small room in your house? What was the litterbox situation there?
How old is your kitty (and what is her name)? Is her poo normal, or hard? My first thought with a kitty not pooping in the box, but peeing in it, would be constipation. I always knew when mine was constipated, because there would maybe be a little poo in the box, and then more poo in other places, mostly on my pillow...
Are you leaving more than one litterbox out? Some kitties develop an aversion to peeing and pooping in the same box.