I can not say for sure, but I think it hasn't been wasted and you shoulnd't worry. (and more: you have more starstones in total than needed, you'd have to waste 5 of them during the Shelter Plane attack to really start worrying).
It would be very hard to do, because you'd need to waste them (if that was even possible) before doing the Luculla escort and before curing Frederic's leg.
Last edited by Chrest; 19/11/15 07:47 PM.