All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
After answering the call of nature, one may use stones, tissue papers and the like in order to remove impurities provided they totally remove the impurities and clean the area.
Therefore, if the tissue paper removes impurities from the area, then it is considered pure even with the availability of water.
However, it is safer to use water since it removes the impurities perfectly.
Allah knows best.