Is that like a belief in unicorns? They forfeited their Holy Orders by joining a heretic and subscribing to a theology that is as different from the one the Church held from the beginning as night and day.
I think I was trying to say they retained a belief in the concept, but let's not be Donatists here and say the worthiness of the minister removes the grace from the sacred mysteries.
I think Orthodoxy has a wide variety of theories regarding the
efficaciousness of non-Orthodox sacred mysteries: ranging from the neo-Cyprianists to those who believe in St. Augustine's belief that heretical mysteries could be valid.