It was a story on Fox news about some scientists in England that did an extensive study and came to the conclusion that probably one doesn't exist.
If you want to read it, this is the link:
http://www.foxnews.com/story/0,2933,581879,00.html?loomia_ow=t0:s0:a16:g4:r4:c0.000000:b-2:z10
For myself, I'm not so sure.
I think I'll continue my own research and keep on trying to find one.
