Would you believe there’s actually a name for the study of “hidden animals” (animals “which might possibly exist in nature but whose existence has not yet been accepted by modern science”)? It’s even got its own peer-reviewed scientific journal: The Journal of Cryptozoology. You can read more about the journal in an article in The Scientist. The journal also has a presence on facebook.
Here’s a few more links if you want to find out more:
Cryptozoo’s Missing Links Primate Center: http://www.parascope.com/en/cryptozoo/missingLinks.htm
British Columbia Scientific Cryptozoology Club: http://bcscc.ca/blog/
There’s also a “reference guide” — I haven’t read it, but it sounds intriguing:
The Field Guide to Bigfoot, Yeti and Other Mystery Primates Worldwide by Loren Coleman, Patrick Huyghe, Harry Trumbore (illustrator)