COs do not necessarily introduce themselves when your case is allocated to them. You will only hear from them definitely if they have something to tell you, or if they require information. Not to hear from them isn't a sign of anything in particular. In any case, since your case only went to the CO the day before the call centre told you of it, it will most likely be some time before the CO sees it. New cases go to the back of the CO's rotating queue of cases (around 100). It will work its way up the queue, then will get its first turn for his/her attention. At that point, s/he will look at your information and send off the first set of queries required to verify your evidence, then your case will go to the back of the line again. Replies will go to your file wherever it is in the queue, and s/he won't see them till it has worked its way to the front again.