J.O.
Kitties can take a little bit of work on a good day, and just like toddlers are prone to accidents along the way.
Either use the bathroom at night, or you can crate them with a little litter pan, some food and water. When I have to do that I find those little aluminum baking pans work great.
This little set back doesn't mean you need to run out and find other kitty options. Look at them like children. When I've had pet issues I find putting it into perspective helps me get through it.