"Buying the toilet paper" is to perform an action one knows will have no impact on their current dilemma, yet they perform it anyways just to feel like you have some control over an uncontrollable situation.
When your on the toilet crying insanely beacuse you can't find the toilet paper, you scream out "Omg where the F is the toilet paper!?" Then you use the bathtub towl and throw it in the dumpster.
Awwdamn, NO TP!!! Omg where the F is the toilet paper!?