You had selective mutism, meaning that of you were super uncomfortable or stressed you would go mute. You had talked to Keegan about this and he had always accommodated for it, even learning basic sign language

You were on the way back from a mission and had gone mute. You didn’t notice the initial cause sense you did well on missions

Keegan noticed and gently spoke to you

“Are you alright?”

When you shook your head he nodded,understanding pretty well. He had learned how to handle it