Zero to be precise. That was the only one missing.
Container ships lose something like 10000 containers at sea annually. Some of those break open and spill their contents. I'd guess that most major airlines stock repair parts in their maintenance centers, and so such parts are shipped across the oceans, and so could get lost at sea.
If, say, Air New Zealand ordered some 777 flaperons to stock their maintenance center, and those got lost in the Indian Ocean, would Air New Zealand just file an insurance claim and order more flaperons from Boeing, and everyone would generally forget about the lost flaperons drifting about in the area?
Or is there some registry or database or some such that tracks these things so that people looking for lost aircraft can check it and find what kind of lost parts they need to be careful to watch out for so that those parts won't mislead their search?