Thank you for the suggestion. We've tried all those lines of inquiry i.e. online form, EMMA, live chat, phone calls etc. In our case we've found USCIS haven't sent our petition to NVC although they stated they were going to do so on our NOA2 dated Feb 1.
Regarding the online inquiry to NVC and reports of receiving a case number shortly after, the conclusion we've come to having monitored all such claims over the last few months is that there is no correlation; it's just coincidence.