Well, this has happened to everyone at some point - you find out there is no toilet paper just after you need it the most. Usually it's not a big deal, even in public toilet room you can wait until you hear someone nearby and kindly ask for paper.
However when such thing happens in a foreign country it might get more complicated, e.g. you don't speak the native language well enough to know what to ask for or you fear the response of people from different culture.
Personally this happened to me only once in a "friendly" place (USA) with culture very similar to what I have at home (Israel) so I knew what you ask for and got help rather fast, but ever since I wonder sometimes what I would do in totally "foreign" place.
So, suppose such thing happens - what is considered best practice? Are there any cultures that might consider such request from innocent tourist as rude or even offensive?