Not going to lie, but you have given zero information in this thread.
You likely clicked it and added a point, hit Esc/Space bar without hitting cancel, went back into your Powers screen and added points elsewhere. The sad part is, Esc/Space Bar doesn't remove points you have assigned.
Thus you used a point accidentally. It happened to me, I lost 10 points doing this looking at the way an ability scales. Raised a bug as well.