Yup. I never had this issue before and its such an obvious move the moment one sees the empty envelope delivered.
Since paper-gate I've been videotaping the packaging and weighing of anything I send. I zoomed in hoping I can see the barcode / number on the box in the envelope and USPS could track the unlabeled box with it but it isn't discernible. I did have exact weight of package and receiver has gone to USPS to see if it can be located but lets face it... It's gone.
If insurance pays out in full and quicky it'll be no harm.
Note that in recent sales I build in the insurance expense into my price even if buyer pays shipping. After paper-gate I would give the option to be "self insured" or pay for insurance but now I just assume insurance in the price. .e.g: These Bellagio $5 barrels priced @ $370 plus buyer shipping will include the $3 insurance premium in the $370.
https://www.pokerchipforum.com/threads/live-bellagio-5.137075/
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--Diz