Alright, THIS IS NOT MINE but I know my case number since I could read it from back of the cashed check. And then I tried pluging different number lower than mine and last one which worked and still showing something on USCIS website as a processed case is this:
On October 19, 2007, we received this N400 APPLICATION FOR NATURALIZATION, and mailed you a notice describing how we will process your case. Please follow any instructions on this notice. We will notify you by mail when we make a decision or if we need something from you. If you move while this case is pending, call customer service. We process cases in the order we receive them. You can use our processing dates to estimate when yours will be done. This case is at our CALIFORNIA SERVICE CENTER location. Follow the link below to check processing dates. You can also receive automatic e-mail updates as we process your case. Just follow the link below to register.
They received mine on OCT 18 and they received this guy's mail one day after and they have already sent them the receipt and his case number is earlier than mine(usuall from USCIS [first come last served]) but people who applied in CA are getting receipt for almost OCT 19 as of today.
So depends on your luck that who is openning your mail and place it in COmputer you get a reciept.
I will try to update again.
Peace