Hey there!
Nice to meet you! I'm Darhyl, an Independent Advisor. I'm sorry you are experiencing this on Microsoft Cashback. I know how frustrating this is and I would totally feel the same way if I were in your shoes. No worries, let me help you sort this out.
Based on the information I've gathered; you will need to report your missing Cashback case by reaching out to Microsoft Rewards Support immediately as they have the tools and resources to properly investigate this case. You may contact them using the link below:
https://rewards.bing.com/support
Thank you for your kindness and understanding! Please let me know if you need anything else.
Best regards,
Darhyl