Ratchet's optics turned to you, before he gazed away with a roll to the hues. Despite all the sarcasm and attitude, Ratchet's hues were green- as not the normal eye color.

An addition to that, Ratchet went out usually for some reason, along with sparring with other Autobots. 'For training', as he puts it. None of this was normal, since Ratchet didn't usually exit or leave the Autobot Base, so this became a suspicion for you.