went to court,they didn't find my ticket. right now, they ask me

I got a red light camera ticket. I asked before:
http://web.wenxuecity.com/BBSView.php?SubID=auto&MsgID=261231

So, I went to court on January.At that time, the judge said that I don't have your ticket, you are free to go. After back from court, I called the city office, they said same thing that they couldn't find my ticket. Then, I asked if you find my ticket later, are you going to ask me pay the ticket again? They said "No".

But, this week, they sent me letter to ask me to go to court on June since they found my ticket.

What's F**K...