Seems like an honest mistake to me. No one yelled for you to stop or red flagged you after you left the line? No one got on the radio to tell people to flag you? Sounds like other people made mistakes as well.

We've seen worse incidents involving starts than this. I never trust the starter to tell me to go. Many times I have been told to go when course workers were still out on course or when a crossing car has not passed yet. Just be aware of your surroundings and maybe you would have seen the guy on course messing with cones.