SITF confirms that this plant is Mystacidium gracile (Aug 2023). There are two listings for Mystacidium gracile in Kew's POWO. This is Mystacidium gracile Harv. and is a leafless orchid; the other, M. gracile (Thouars) Finet, is not leafless and is synonymous with Angraecum gracile. The flower size is right on the money and the photo almost exactly matches the image of M. gracile Harv. in the IOSPE. Supporting closely matching photos can be found in the OW and many on the internet and in the orchidroots.com.