This is something I found, years ago and thought was hilarious...enough that I've saved it. I haven't read it in forever, so hopefully it doesn't offend anyone or break any of SWF's rules...
"This may save your a** one day...
---Hopefully, this has never happened to you. It can be among the scariest situations in which you'll find yourself - parked on the throne only to discover that, yes, there's no toilet paper.
Now, normally you'd make sure that all the necessary supplies were present before beginning the evacuation process, but sometimes mitigating factors force you to omit this part of the procedure. For instance, you're sitting at your desk and last night's enchiladas with extra jalapeños decides that it's time to make a hasty exit. You stand up and, while trying to contain your terror as best you can, do an accelerated power walk to the nearest restroom. Normal pleasantries are forgone, obviously, as you scamper to the nearest commode to expel the vile spirit. Rushing in, you pay no attention to seat covers, toilet paper, even the locking of the stall door. Dropping trow, you violently lob yourself onto the seat and relax that oh-so-important muscle. Sweet relief.
And that, my friend, is when you'll come to the realization. The bum-wipe has been depleted and you're sitting there wondering how the hell you got into this mess in the first place. But fear not, my friends, you do have options. Now, bear in mind, your goal here is not to get absolutely clean. You merely want to give yourself a good once-over, enough to where you won't soil your under-lovelies in transit to the next stall.
Seat Covers - This is your first choice. Though, if the cleaning staff has failed to replenish the toilet paper, chances are you're staring at an empty seat cover box as well. If there are seat covers available, they will do just fine. They will be quite uncomfortable, but they will get the job done. Just make sure you realize that seat covers have an entirely different feel and, if handled incorrectly, could do some minor damage to the old o-ring. On the plus side, these are flushable so you won't need to make an embarrassing deposit into the garbage can as you leave.
Check Your Wallet/Pockets - Got an old business card in there? Perhaps a receipt from the grocery store? Remember, desperate times call for desperate measures. If you do choose to use something of this variety, please know that it is possible for something this small to go down the tubes when flushed (though, it could also stop it up). This option also runs the risk of rear main seal damage, especially if you choose to employ a business card or something else with similar rigidity.
Phone a Friend - Normally, I'm a strict (almost maniacal) opponent of any type of conversation in the restroom, but this is serious business, so an exception must be made. If you happen to hear/notice a neighbor in an adjacent stall, you might ask for help. In order to avoid actually saying anything, you could simply cough loudly and toss the empty roll under the partition to indicate "man, I'm in serious trouble". Any man with the slightest bit of compassion will either lob over an extra roll (if one is available) or hand you a generous wad from his side of the wall. This Samaritan will also, hopefully, know that this is never to be spoken of again. If he just fell off the turnip truck and has no idea what to do about an empty roll, a simple loud cough followed by "help" will probably do the trick.
Absolute Last Resort - If you've arrived at this step and have exhausted all previous options, I must warn you: this is disgusting and you will cringe at the thought of it. But, again, you should be more concerned with swabbing the deck than with anything else. Your move right now is to remove one of your shoes, followed by the corresponding sock. That is your weapon. I know, it's repulsive - but, again, consider your situation. Once you've finished, it is imperative that you dispose of the soiled article and get the hell out of the bathroom as fast as you possibly can (not without washing your hands, though - especially after what you've just done). Your only other option is to leave your current stall, put the sock in the trash, and relocate to a properly-stocked stall to complete the cleanup process (and thereby avoiding incriminating yourself). Either way you choose to handle it, it's important that nobody see you carry a poop-laden sock from the stall to the garbage. If they do, look forward to chiding and crap-based nicknames for the coming months."