The new CO will be doing like they all do - working their cases in rotation. They take the first, do everything they can for the time (sending out queries, or ticking off replies), then put that to the back and take the next, then the next, then the next, and so on. They don't take any file out of order. Your reply will have gone to your file wherever it is in the queue, and the CO won't see it until it's your file's turn to be looked at again. INZ officials' job focus is to process cases - they are not meant to send 'empty' emails (e.g. 'Dear Mr Applicant, I have not yet had a reply from your university so I have not been able to do anything new with your case, and it is waiting in the queue') as this takes up time when they should be working something that HAS arrived and CAN move someone's situation on. Therefore, quite often, you don't hear anything for some long time (and it always SEEMS long to the person waiting).