I was giving my xt660 its bi-annual thorough clean so we got very up close and personal. I noticed a bolt had come undone and fallen off!.

The bolt in question is one of two which holes the cylinder head cover plate in place (the clutch lever side- LHS). HAs anyone had similar experience.
Is it just a question of fitting a new bolt or is there more to it...?

yes i ended up with new bolt. my friendly yam dealer had not come across this before, then again not many sell many singles.
the moral of the story is it pay from time to time to get up, close and personal with your bike