This happened to a friend. Baby was misdiagnosed with reflux when it was actually an oversupply of milk and a fast let-down, so baby was spewing from being overfill, nothing to do with reflux at all. She fixed the oversupply and the reflux resolved. Could that be a possibility in your situation?
If your baby presented with symptoms of lactose intolerance (and this was why you're on that formula) then this scenario is actually very likely. Would need more info on baby to be sure, however.