It's been a few days since your post. Has it happened again? I hope it hasn't and she's using her litter box again.
Maybe your kitty is reacting to the relocation of her litter box. You know how cats HATE changes. They like everything to be in exactly the same spot. It makes them feel safe and secure.
I know some people who lets their cats poop in the bathroom near the drainhole. They'd just wash it down with water later on. It saves them money on litter sand. I wanted to do that but I can't stand the idea of having the poop/pee sit there for 8-9 hours until I'm home to wash it away