From a museum this time.
It's not unusual to find new species in museum collections - the world's largest gecko and longest-legged spider were described that way. (How did the spider get overlooked? I am trying to picture a curator saying, "Ho hum, foot-long spider - file it over there.")
Now we have this little fellow. The New World's newest mammal is the olinguito (Bassaricyon neblina), which has actually been in zoos but has been overlooked because it looks fairly close to another species. Kristofer Helgen, curator of mammals at the Smithsonian's National Museum of Natural History, found the specimens in Chicago's Field Museum that sent him on a quest for the living animal: and here it is, from Ecuador's cloud forests.
Welcome, little guy.