Is the sphagnum just a top dressing or is the plant potted in it? Are you sure your roots are OK? Might be why you only got one flower.
It is planted in clay pellets, just 1cm sphagnum moss. Roots are in good condition. Most of my cattleyas lost buds before they bloomed. What I suspect is that this year the building where I live was in the capital repair, a lot of vibrations and noises from pneumatic hammers.