i have never heard of this, but in a way it makes some sense. see, if your prostate is stimulated, then you can ejaculate. if you just happened to stimuate your prostate, you may have ejaculated as a result of that stimulation. i don't think that this is an indicator of anything wrong.
it may have happened during your bowel movement and you didn't even know it (not so much as a result of your wiping). i had a b/f once who told me that a doctor did a prostate exam on him and that when the doctor did that, he "shot".
maybe you just had a skillful poo...hehehe.
jasmine