Hello The classic missing needle often occurs where people remove the needle from an engine that lives in a box, so it will fit in without poking a hole in the box lid. It gets lost and you get a new engine in the box with no needle like an ETA 29 I have, at least reproduction NVA's are being sold on Ebay but pricey.
Probably more common are the broken or bent needles in used engines that are missing , the owner probably intended replacing, but never did.
Missing prop drivers especially on splined or loose keyed shafts are annoying too. (I epoxy them on the worst offenders to save loosing them when using an electric start as they often shoot off to never be seen again).
Regards Gerald