hidden and or racial tech areas

[jars_u]

Once you destory/capture another empire that has a special tech area - say the "Crystal Empire" which has the crystal armor that channels damange into shields, why is (at least in my exp) that tech area not transferred with the rest of the technology. Also tried to capture and Analyze ships with said tech area but did not net any new tech areas with which to design my own ships. What am I overlooking?