I bought this from a reputable orchid shop, and it is labeled a Phal. Frenchy's 'Plastic Yellow', but what I didn't notice until I got home is that it doesn't have a lip!
I've been through nearly every pic on Phals.net and can't find any other Phal without a lip. Is it possible that it fell off???
It may not be easy to see, but there are just two barely there nubbins where the lip should be...
The lip was either broken off or the flower grew out deformed. It's almost certainly a one time thing.
It is possible that your plant is a mutant (which can happen even with clones), but it's not terribly likely. Stable mutations resulting in missing flower segments are unusual. More common are mutations that result in the petals partially or fully turning into a lip, or the lip partially or fully turning into a petal.
I have seen mutations before, when a plant is struggling. I've also noticed it on one of my Phals where a Keiki bloomed perfectly at the same time that the mother put out deformed blooms.