Marthak...
that is correct... you won't know your RD without your receipt notice. normally, employers/lawyers let you keep your original receipt notice because, in case of i485, you are the applicant (in case of i140, the employer is the applicant, you are the beneficiary). so you might want to ask your employer/lawyer to give you either your original receipt notices, or at least, their copies, which comes in useful if you are applying for EAD/AP by yourself, or travelling outside the u.s.
however, it is not devastating if you don't have/get your receipt notices/copies, as long as you know your LIN numbers. similarly, an RD is not as important as ND.