Here is a thread started by me when I was in a similar situation. In my case I think it was someone who got caught on security video breaking into a bunch of cars on my block one night including mine. I wasn’t going to be much of a witness since I didn’t see anything, and all I could say was that I kept $40 in emergency cash in my car that was not there when I checked after the incident. I’m not even sure that it was about this since all that was on the notice was the time and place I needed to show up, and the name of the defendant which I didn’t recognize. I’m assuming this is what it was because that was my only brush with law enforcement.
The end result (not included in the thread) was that shortly before the trial I realized that I had lost the paper that told me when and where I should go. I tried calling the court to ask, but they didn’t seem to have any way to look me up, so I ended up not going. Other than that first piece of paper in the mail (non-certified) no one ever contacted me.