I had both upper timing covers off when I lost that metal part.
I haven't removed the lower timing cover, so I can't comment on that.
You could try (after removing belt, fan, etc) to turn the crank by hand (very slow!!!), and if it doesn't turn one way, then you know it's lodged between the chain & crank. But you incur the risk of it falling further down, if it's indeed lodged in there, if you move the chain in the opposite direction (the chain goes down at an angle, and is wide enough to keep a small part wedged between it and the crank).
The space is very tight, and I couldn't work any light in there.
The reason I was lucky, was because I "swept" probably the whole bottom of the upper oil pan without any luck. The only possible place left was... the chain (or down one of the holes to the lower oil pan).

GL

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Stable: e92is, e46 M54B25, e83 N52, e53 N62 - sold, e39 M54B30 R.I.P.