We have been doing the same. Infact we sent out an email to the research email I'd but no help. All they say is we have your form copy and we will contact USCIS to locate your approved petition. When we checked with USCis two days back , they still haven't sent out our petition. I have already completed 60 days as per my NOA2 receipt date (10th March) ... It's extremely disappointing the way they are working. Are you serious April NOA2's have started receiving their case numbers ???