Before toilet paper was invented and made people used to wipe with corn cobs, tree leaves and even used catalog pages.
The Sears catalog was widely used in outhouses for wiping with when people were done reading with it and they would hang the used Sears catalog up in the outhouse and tear pages out of it to wipe with and then dispose of it down the outhouse hole.
Sears knew about this and when Sears started printing their catalogs on glossy paper, people actually wrote in to them to complain because they could no longer use the catalog for toilet paper.
Other things that people would use for wiping with before toilet paper are stones, moss and even other catalogs and newspaper pages.
Some people would also use washcloths or even sponges on sticks to wipe with before toilet paper was available.
If you have no toilet paper you can use a washcloth and get it wet and wipe your butt with it and then wash it off and throw it in the washing machine afterwards.
Or you can use baby wipes instead which can also get you cleaner or paper towels but throw the paper towels and baby wipes into the trash and not into the toilet as it can clog the toilet.