I was riding my 2004 wr450 a couple weeks ago and my buddy noticed a quick puff of white smoke out of my bike. Later I noticed a small dripping of coolant from the radiator. Since I couldn't repair it right away and it was slight dripping and somewhat intermittent I did another 50 mile ride on it before I pulled the radiator off. When I did I noticed a plug missing on the cylinder next to the exhaust connection. From looking on-line I think it is a cap to access the cam chain. Has anyone else had this happen? Do you think I may have done any damage riding with it out?