You may be able to get USCIS to reopen this case based on their error. However, they are not going to take your word for it. The ideal situation is where you have a complete copy of what you sent, AND can confirm delivery (this means you used FedEx or UPS, Priority Mail, Express Mail or Certified Mail and got delivery confirmation). Without that, you are probably better off re-filing.
My response to your question is general in nature, as I don't know all of the facts of your case. You should retain an attorney experienced in immigration law to review all the facts in your case in order to receive advice specific to your case. In addition, my answer does not create an attorney/client relationship.
I guess you need to hire an immigration attorney and stop dealing with people who misinform you even if they work for USCIS. Short of that only G-d can help.
The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter,not should it be viewed as establishing an attorney client relationship of any kind.
Mr. Segal is correct that you need to hire an immigration attorney badly. This is not a do-it-yourself project and you are getting terrible advice. Look for an immigration attorney here on Avvo with the Find a Lawyer tool
The information provided in this answer does not create an attorney-client relationship and is not considered to be legal advice.
This case is going to be complicated. Depending on your circumstances, it might be quicker and cheaper to re-file rather than fight about the denial. Meet with an immigration attorney before deciding how to proceed.
Please note that this response is for informational purposes only and does not create an attorney-client relationship.