Being arrested isn't criminal. Being arrested and having the courts decide you're guilty IS.
Many times, a police officer would have the reasonable belief to make an arrest. But the COURTS must still decide whether the person truely committed the criminal act. (Until the courts decide, it's not officially criminal.) Being arrested is only the first step.
Here, the courts never decided anything. That means that there's the possibility that you were falsely arrested. For that reason, you may have just cause to wipe if off your record (or opt for nondisclosure).