I've been playing, and really enjoying this game. I've just started a new mission, and for some reason, my helicopter strike building was unavailable; just greyed out in the tech menu. I assumed it was a bug, surrendered and reloaded the same mission. This time, I can't build ammo supply. Tried resetting again, and this time it's shotguns that aren't available.

I'm assuming this is a bug? I've tried to figure out if maybe it's a mechanic of some sort but it really doesn't seem like it.