I have a 2005 Kawasaki Concours with 26,000 miles.

When I started to do a valve adjustment the left side exhaust valve on the #1 cylinder was missing the screw and lock nut. I found the screw and lock nut in the upper part of the head and no visible damage could be seen. I was able to check and adjust the right side valve fine. But, when I tried to check the left side I could not even get the feeler gage under the tappet. I took that screw completely out and there was still no clearance to get the feeler gage in. I did not move the camshaft and the cam lobe is pointing away from that valve. Apparently there has been some damage done, but what? How do I determine what has happened and how do I fix it?