coolant leak?

I pulled my bike out of the corner today, took it for the first ride of the year. When i was backing it out of the garage there was a little drip trail, then a puddle under the bike, not alot, but a bit, maybe 2 tbsp. The coolant seemed to be coming from the left side of the cylinder, there is a little boss with a hole, it looks like there should be a bolt there but there isn't. I looked up the microfiche and sure enough there is no bolt to go in the hole. What is this hole? Why did the coolant leak out of it? The bike had been sitting for about 4 months, I may have started it once over the winter. I went for a ~2 hour ride, no coolant loss, bike ran fine. Is there a problem?:confused: Thanks in advance.

add some pics so that we can get a better idea.

I have the same problem?! I have coolant dripping out of that hole? Any one know what it could possibly be? The hole is on the bottom of the bike right above the exhaust piping...