1: Never interrupt an animal when they are going to the toilet-it confuses them
2: Has your cat been vomiting?
3: What food is it on? Does it get outside much? Does your cat eat grass? It has natural folic acids which ease stomach problems, and is a natural laxative? When had your cat last been to the toilet?
4: Sometimes cats stools are loose. Sometimes there is no medical underlying issue, just like sometimes our stools are loose. If it becomes frequent, then of course seek veterinary treatment, however, I honestly would not worry if it was just a one off.