My cat is a fuzzy little jerk just like yours. I had tried putting the TP behind the toilet on the tank, on the counter, wherever. Cat still got to it. Tried to keep the door closed, but my roommate is a jerk and never remembers to close the damn door.
Then I found this weird thing on amazon. It's like a little elastic locking gizmo for the toilet roll, you just unlock it to unroll TP, then lock it back up when you're finished with the business. Voila, no more wasted toilet paper.
I can finally go back to buying the glorious charmin strong. My cheeks yearn for it.
You could try something like the TP Saver, but I think that would be pretty easy for an adult to bypass.
My best suggestion is to put aside toilet rolls when they're down to an amount that wouldn't clog the bowl. Put one of these in the bathroom before the party starts and store all other TP in another room. When one short roll runs out, replace it with another.
Maybe post a note as to why you have to do it this way. Other guests may mention that they've had the same problem; and the list of suspects can be narrowed down that way.
I've heard of this product, but never tried it. Worth a shot?