I spent a bit o time checking through the Pleurothalid Alliance site a few hours ago, clicking till my hand hurt. I gave up. That sure is a cool little pleuro though. How small are those flowers? Relative to the wire in the photo, they look like a millimeter at best.
it looks like one of the clear yellowish forms of pleuro grobyi, which is "relatively" common in cultivation in the U.S. But perhaps this is a trick question.............