In my experience it is normal for the flower to drop. Sometimes, it seems premature as it hasnt started to wither. I usually just set it on the kitchen counter until it shrivels up.
I also tend to use higher light than for Phals with my Phrags. I have found they can handle it and many growers have them in light similar for catts. Some I've learned need higher light to bloom. I have not had any negative side effects of higher light either.