One of the cardinal rules of
camping is as follows:
The backpack that {falls in the water | gets eaten by a bear | spontaneously bursts into flames} will be the one containing all the TP.
Much suffering can be avoided by the simple precaution of bringing a roll of Emergency Toilet Paper stored in a zip-lock bag in a side pocket. To score experience points with the rest of your party, don't tell anyone about your secret stash. Then, when the inevitable disaster occurs, let them wail and gnash their teeth for a bit, then reveal your Emergency TP and bask in their adoration.