Upon closer inspection of my chain I found that, indeed, one of the side plates had totally detached from the connecting pin! The reason I didn’t notice it before was that it was on the inside. Good thing I didn’t stay in the race for the final sprint, I probably would have snapped my chain! The last time I broke a chain was when I was in college while sprinting across an intersection on my mountain bike. When it snapped, my weight was on the front pedal so it threw me over the bars, chin-first into the pavement. I remember walking back to campus with my bike on my shoulder and blood dripping down my chin. I think I got around six stitches that time. I’m glad today didn’t end like that!