CPS Lens Maintenance Record

If a lens is sent to Canon CPS for maintenance/tuning (no repair), can anyone ask for its service record from CPS, e.g., by the serial number? I've asked sellers who advertise the lens has been cleaned by CPS for some proof, but their responses had been a variation of they no longer have the CPS receipt.

(edit: not saying that CPS maintenance is a must have, but if a seller advertised that it's been done, being able to verify it would be nice).