Glad to hear you're okay, Cloudchaser. I'd have to agree with pdwestman: you had plenty of time to recognize and react.
Don't take that as an insult, though. It's happened to me and probably most people on here. I was fortunate to not rear-end a pickup/trailer not long ago when my attention was on a vehicle merging from the left and I was not expecting the pickup to stop since they were only required to yield. I almost had to go to Walmart to buy a 6-pack of clean underwear after that one. It was close. My front tire actually hit the back of the trailer when I stopped.