From what you've all written and I googled, I'm convinced that it's highly likely to be a mossiae. Today the flowers have a noticeable liliac-like smell.
The plant flowered from an almost-dry yellowish sheath. The growing and resting periods are not very well-defined, it completed the flowering pseudobulb in mid-winter after a larger pseudobulb got sunburnt in the sheath. It gets fertilizer and water as long as there's new growth around.
I think I didn't rot the plant as my growing conditions are a bit dry and I never fertilize heavily; < 0.9 EC in every watering except for very cold days when the windowsill is cool.
Although it's a first blooming, the flowers are more than satisfactory for a plant living in a 500ml ice cream box