Chances are you’ve bought something from Amazon in the last few months (yes, we are all hypocrites, also there’s a pandemic on). Try searching your email for one of those orders. For me, that’d be “cat flap” or “chilli oil” or “airfloss”.
https://mssv.net/2020/08/16/digital-sight-management-and-the-mystery-of-the-missing-amazon-receipts/