I got asked something similar once, i witnessed a mass fight in the middle of town, and they asked me for evidence 2 years after the event. Bearing in mind i lamped someone, and was very drunk i couldn't remember anything.
I turned up to court for the day of hearing, and was told they forgot to book a judge so it was cancelled.... WTF?!?!? So i left. they asked me to go back again, and i said no, i wont be attending, i'm not waisting anymore of my time, and i couldn't remember anything anyway as it was 2 years ago. They said if i didn't go, they would come to my place of work and arrest me. I told them to try it, and see if they could find me.
Never heard any more from them.
Good luck dude, i'm sure it's nothing to worry about.