Probably being researched in a different barracks. 

With the barracks selected, why isn't the button for that tec displayed?

Barracks, after P3

Hello, I haven't use too much this civ, I played them, made all techs and buildings and couldn't see where I can get Reform Army tech, I have seen this unit in some games, so I know is not a kind of bug or something, it is me missing something maybe. 

This user cursed me, tried to harass me on social media outside of the game, and wasted 55 minutes on pause on purpose...