According to my experience, USCIS does NOT resend receipts (or it is really difficult to make them to resend a receipt). I have never got mine... I submitted 3 I-485 applications, 3 APs and 2 EADs, all in one package, and they managed to send all the receipts and approvals to the correct address except one - somehow they sent my I-485 receipt to the old address from my I-140. When I called TSC (it was a good old time when you could call TSC directly), the representative told me that they will not resend it. A friend of mine was in the same situation, but he was able to convince them to send him at least some kind of officialy looking paper with receipt # (printed on plain white paper, not a form I-797).
Although they DO resend FP notices, RFE etc (also based on my experience - my FP notice originally went to the wrong address too).
But don't worry too much - you do not really need a 485 receipt. As long as you know your receipt #, and have an evidence of your status (EAD works as proof of status), you are good. The receipt # should be on your cleared check, even if "WAC" letters are missing - try to find 10-digit number on the check - look at both - front and back. When I applied for 2nd EAD, I printed out web-page with online status to attach to the application instead of I-485 receipt, and it worked. I would not spend a lot of efforts to get an actual receipt - definetly does not worth it. What do you need this receipt for anyway?
Of course, if you could not find your receipt #, do something - perhaps your attorney can initiate an inquiry to the SC. Or you can go to your local CIS office, and they can send an inquiry for you too...
