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The insurance rarely covers accessories, or as you say the accessories were with the phone at the time of loss or theft.
As you were responsible for losing the earbuds, there is little you will be able to do, they are not covered by insurance and any replacement will need to be paid for by yourself. Perhaps add them to your Christmas wish list and Santa will replace them for you.
Have you lost the whole thing i.e buds and case or one of the buds.
There is a findmybuds option but that just makes the bud emit a sound.
If your Vodafone Insurance won't cover the loss then perhaps look at any applicable Home Contents insurance.
If you haven't any then I'm afraid you'll have to buy another set.
I have the Samsung Buds Live and Apple Airpods Pro so I know how small these buds and cases are.
Current Phone > Samsung Note 20 Ultra 5G - SM9860 Snapdragon.
Samsung One Ui 3.0 / Android 11.