Please Help! Court Record?

Sorry that I can not type in Chinese.

I was charged for shoplifting once in New Hampshire last year. It turned out to be a misunderstanding and the case was dismissed. The general lawyer helped me to file an annulment application and it was approved. I was told that the record was gone. I filed green card application this year, and now USCIS asked me for the file showing that the case was dismissed. However, when I went to the court, they told me that since I annulment application was approved, there was no record at all. So they could not give me anything. I am not sure how USCIS can still see the charge. The court said maybe the record was not removed from the police station.
My question is
1. Is it possible to get any file from the police station showing that the case was dimissed?
2. The answer to question 1 is no, what kind of material can I give to USCIS showing the case was dismissed? I got a file from the court saying that there was no record, does that help?

Thanks a lot in advance!Any advice is highly appreciated!