Here's a picture of the foliage - canes about 64cm long (just over 2 foot), flower itself is about 1.5cm across, lasted maybe a couple of days - when I went to measure it today it is folding up. Every other time it has flowered in pairs - so maybe it is just that the other bud died in this particular case.
As an aside, having seen your post on the dendrobium alliance, thought you might like to know there is a Dendrobium pentapterum growing just next to the roots here on the same tree - here's the pic: