Undefined CoS Marked As Used

Dear Members
I am seeking advice on the below situation and any valuable comments are highly appreciated.
My company issued an Undefined CoS to a potential employee who applied for his visa back in Jan 2024.
We received a request from the Case Worker to amend salary on the CoS by adding a sponsor note to the CoS for them to confirm the request has been actioned.
Now the problem we have is when we want to look/Search for the CoS to add a sponsor note the message appears "No CoS was found with name or number".
The CoS issued is still there on the SMS system and the status is showing as USED.
Can someone guide me how to add a sponsor note the undefined CoS when the status show as USED?

I look forward to hearing from all respectable members