If they choose the honorable decision 'A', the next time they stumble into a bathroom and the TP is all gone, they will immediately take note of it before going to the bathroom. Should the person make sinister decision 'B', then the next time they go into a bathroom without TP, they will carelessly plop down disregarding the supply (or lackthereof) of TP, not realizing until it is far too late to turn back.
b) After using the last of the roll, Suzanne walks out of the bathroom, thinking: "Whatever. The next person can get it". Later that day, Suzanne's intense diarrhea flares up, and she makes a beeline for the bathroom. Barely making it in on time, Suzanne pays no attention to the sparse TP reserves in the bathroom stall. When ready to wipe, Suzanne's eyes fix on the depleted roll of TP. It is then that Suzanne realizes that her bad TP Karma has caught up with her.