When looking at the audit trail you would not be able to see the original Client-Matter because it will only list its current properties. If the Client-Matter was changed you would see a CaseOID in blue.
To find the Client-Matter where the CaseOID is linked you would need to open File Maintenance Matter Manager. Right click and choose Select Grid Fields. Drag and Drop the OID field onto your grid. The OID field is the CaseOID you saw in the Audit Trail record.