A customer created a case using web to case. They contacted phone support to get an update on the cave two days later. The support agent cannot find the case although the customer is positive that…

Validation rules prevent records from being saved if they don't meet criteria, which could prevent a case from being created, but the audit trail would indicate if a validation rule was recently created or modified to troubleshoot this specific problem.

The contact email address is data associated with the case, not a tool for troubleshooting why a case might be missing entirely from the system.

The Setup Audit Trail records all administrative changes made within Salesforce. If a Web-to-Case setting, an object's field, or a workflow was recently changed that inadvertently prevented case creation or visibility, the audit trail would show those changes, aiding in troubleshooting.

Assignment rules route cases after they are created; if a case isn't found, it implies it wasn't created or saved successfully in the first place, not that it was mis-assigned.