yech... I can't really believe that we're having this discussion... TP is ALWAYS near the top of my packing list...
and even in the event that all the TP is gone... like if you didn't waterproof it well enough and you went swimming with your pack (been there, done that)... hell, whay do you think God gave you 2 arms? So that you'd have 2 sleeves to wipe your ass with!
and if you're wearing long pants, why, you'd get instant bermudas or shorts! And surely tou have some spare clothes in your pack... a T-shirt even?
And if you're really so environmetally puritanical and don't want to befoul the environment... then do what the SAS do... carry a roll of clingwrap in your pack: layout a piece of clingwrap before you ****... you can **** into it, tear off a piece and wipe your ass with it... then roll it all up and take it with you for disposal when you get home. This is so you leave no trace of your *ahem* presence behind.