Please make sure you didn't delete this assignment in SharePoint.
SharePoint Settings > Site information > View all site settings > Site Collection Administration > Recycle bin
You could find deleted items in Recycle bin.
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Hi @Poitras, Renee (ASD-N) ,
You could try to search this assignment in Audit search. Microsoft 365 admin center > compliance > Audit. You could get more details in Audit search.
Hi @Poitras, Renee (ASD-N) ,
Would you tell me whether your issue has been resolved or have any update? I am looking forward to your reply. Thank you.