This is pretty incredible but I am willing to bet that it happens more than we think. Many scientists will start a research project at local markets to ask the natives where to find certain animals that are being sold there so I imagine that new species riddle these local markets.
http://articles.cnn.com/2010-11-10/...zard-species-reptiles-scientists?_s=PM:LIVING
http://articles.cnn.com/2010-11-10/...zard-species-reptiles-scientists?_s=PM:LIVING