Speckled feeder roaches/ woodies are what they call 'False live bearers" They develop the egg sack inside their body and when they lay them they almost hatch straight away. Sometimes it happens that the female prematurely lays the egg sack these eggs will not hatch. In general the woodies will hatch within 5 minutes after laying. Normal cockroaches lay diffrent egg sacks they generally have the egg sack attached to them for several days and then they deposit them inside a crevice or any dark place. The eggs will then develop and hatch. Your female would have eaten the infertile egg sack for sure as this would have been a good protein meal.