What Could I Have Done Differently To Avoid This Accident?

I was given a 15sec penalty for failing to slow and causing a collision in a yellow. There was never a yellow flag displayed in my car or by the marshals going into this turn. Was the 15sec penalty for causing a collision under yellow warranted and could I have done anything differently? I am not denying that I made contact with the car, obviously I did. That's not what I got the penalty for. Let me know your thoughts below.