Thanks, that's what I am thinking.
It kinda of fell through the manifold, not into or down into not like if I stuffed it into the intake or something. On my 560sl there are openings, crevices I call them, in places on the manifold that just seem to drop off into nothing. I assume, unlike on a Ford -V8 for example, that there is just nothing under the manifold and it is raised up to dissipate heat.
If I thought there were moving parts or high vacuum that could suck a bolt into the engine, I would have stopped immediately. In this case, it sort of seems harmless, but I wanted to ask.