Good catch and fix on your part! I believe this is the 3rd incidence I've read of on this exact issue on the Command series V-twin Kohlers. You're lucky it didn't break the boss that the rocker hold-down stud threads into and lucky the pushrod didn't smash the rocker arm through the plastic valve cover. That's the usual result if I recall correctly. So much for a maintenance free, hydraulic lash adjuster equipped "premium, commercial grade" engine! I guess the moral of the story is, any undue noise or power loss, pull the valve covers and take a look. I'd probably loctite those babies on even.
Joel
Joel