The Fantasmic Dining Package has to be booked as such and should state on your dining reservation confirmation. On my confirmation page for just that reservation it gives the dining confirmation number, then right under it it says "Fantasmic Dinner Package" and under that is the name of the restaurant.
However, if I pull up my entire list of dining reservations, there's no mention of the Fantasmic!DP for that reservation.
It sounds like you called to reserve it. Did the Cast Member ask for a credit card? Unlike a regular reservation for Mama Melrose the Fantasmic!DP requires a credit card guarantee. If you didn't have to give a cc number, the CM didn't book a F!DP for you.