If you were arrested, a record of the arrest appears in the FBI database. if you were arrested, then you were scheduled to be arraigned a short time later. If you were actually arraigned, the charge should show up on your CORI. It does not matter that this was the first time you were arrested.
It sounds like you received pretrial probation for 6 months, did the community service and then the charges were dismissed at the end of the 6 month period. When you checked your CORI, did you do so using the state's iCORI system, or did you use some other means?
Another possibility is that you were not actually arraigned after you were arrested, but rather the arraignment was continued to a later date to see if you could do the community service and stay out of trouble for 6 months. That is not a common outcome, but I have seen it happen on occasion. If the matter was dismissed prior to arraignment, then it would not show on your CORI. The best way to find out is to check the court docket itself - the docket will say whether you were arraigned or if the charges were dismissed prior to arraignment.
I agree with the other attorneys; you do have a record. It may not be disseminated to the public because there was no conviction ( new CORI law effective May 4, 2012). Certain requestors will be able to access your entire record, even matters that are dismissed. The record you received may have shown nothing because the case was dismissed.
If you were arrested, you may or may not have been arraigned. It is not uncommon for a person NOT to be arragined on a minor charge, and have the matter go through "diversion" where you would have the case open, do community service and keep your nose clean, then have the case dismissed without it being on your record. Check to see if you had diversion...then, no, you would not have a CORI record.,
Best of luck!
Valerie Semensi @ 781.383.1940