The sponsor can try to contact the Call Centre to see if they can find the file number in the in-Canada notes . . . I say have the sponsor call because the number is within Canada, and if you're the applicant and you're in Canada and you call, the agent will give you the third degree and then probably tell you they can't tell you anything. So, it's best for the sponsor to call - they tend to try to be at least a bit more helpful to sponsors. Also, see if you can inquire via eCAS using the sponsor's information and client ID#, and get anything. There should be a link to the processing info for the applicant, and you might find a file number somewhere there. It should start with a letter, and then about 7 numbers.
If you can't get it, try to send the request without the file number . . . just indicating London . . . and maybe note the sponsor's client ID number somewhere so they have a cross reference. They should be able to track down the notes without the file number if you give them enough other info.
Here's a list of addresses to submit the request to. If the applicant is in Canada, they can request their notes via the Privacy Act, and
send the request to the Privacy Coordinator in Mississauga. If your sponsor is requesting the notes, it has to be a Access to Information Request, and that is sent to:
Access to Information and Privacy Coordinator
Narono Building
360 Laurier Avenue West, 10th floor
Ottawa, Ontario
K1A 1L1