Well Hasselhoff... whether you call it 'luck'...
First, that suspected 'male' you have in veg is more than 99% likely to be female. What most likely happened is simple. The grower who grew your Jack may have done one of the following: Let the room get too freakin' hot, had a light leak, or allowed the plants to go over-ripe. This caused at least one female in that room to go hermaphrodite. Since you said you had a wicked lot of seeds in the bag, it may well have been THAT female, because seed concentration on buds in a crop diminishes with increased distance from the pollen source. A female can produce pollen, but she physically CANNOT produce Y chromosomes; therefore, the chromosome pattern XY which is responsible for male gender expression is an impossibility.
That's all well and good with one little problem... she also passes on her likelihood of herming.
So ESPECIALLY with 'feminized' seeds, pay EXTRA close attention to your grow conditions. You must keep a regular photoperiod, with no light leaks, no stress, and no 'hot spots'.