There's something missing in this account.
If a PCN is issued by a CEO on the ground, then it should be affixed to the vehicle.
If he has begun to prepare it, and the driver drives off before it can be affixed, a postal PCN may be issued to the registered keeper. But your photos in indicate the vehicle pulled into space and parked, giving the CEO the opportunity to affix it, in which case a postal PCN should not be issued.
If the offence is filmed by camera, then the ensuing PCN is posted.
Have you kept any of the paperwork?
Could you take a screenshot of the case history from TfL's website, please.
Sorry about all the questions, but without having a full account it is difficult to discern the next step.