I had the same thing happen to me last sunday (8/8). I was out for a ride and my coolant temp light came on twice.
The first time happen while I was idling at a stoplight in town. I had just come into town from some mountain twisties, running 6k-9k (I notice alot of engine heat at these rpms). It was a very hot day and had rained in the morning, so very humid as well. I pulled over and let the bike sit for about 20 minutes, since I needed to cool off as well. Bike started up just fine, ran smoothly, normal.
Second time happen as I was heading back home, probably an hour after the first. I passed a campsite next to a river in missouri and stopped to check it out. As I slowly cruised through the site, the light came on again. Engine was still running fine, so I just hopped back on the highway and popped up to 55, but kept my rpms low as possible (~4k). About a minute after this, the light went off. Again, engine sounded fine, although this time, I was wearing my earplugs and should of checked to see if the fan was running.
The rest of the day went fine, with no more problems. Next day after I got home, I checked the coolant level, exactly between the two lines. Oil is fine. Fan spins freely. Radiator looks fine too, aside from a bug or two that I removed. Going to take it for a quick spin tomorrow and see if the fan kicks on like usual.
Any ideas, aside from it was probably just a hot day?