If you have the tappet cover removed, you can look around inside the tappet galley to see if any lash cap is down in there. That's as far as it could drop, if it stayed in one piece.
Chas is correct on the caps last time I used a little heat and they came right off. ERC
Your eyes must be better than mine.In the two pictures of the intake valve I think I clearly see the two split collars and the end of the valve stem?I picture (in my mind) the stem cap as being a cylindrical disk that fits nicely into the pocket in the upper part of the valve spring retainer.It should have a nicely ground finish on both faces. IMO, if it were in place I wouldn't be able to see the end of the valve stem or the split collars but what do I know?
I cleaned everything in the head and lapped the valves. When I brought it in for assembly they said the seats were too wide, so I asked them to fix that.