Not really sure what you're saying here - are you saying that the first tick of a MF cast can miss but it will continue to channel and the 2nd and 3rd ticks can hit? If that's what you're saying, that's incorrect.
If a MF misses, the whole spell misses, not just the first tick - the mana is spent, as well as a GCD, but the spell does not continue to channel if it's a miss.