My Change of status from H4 to F1 got denied. I had received a RFE. Reason for denial being RFE documents not received in the stipulated timeframe. I had sent the documents within a week of the RFE which USPS did not deliver. I do not have proof in terms of tracking number or anything similar that establishes that I had sent the documents. The notice that I received from USCIS states that I need mailing proof to file a PTR. Do I have any options here? I am out of status now and in all likelyhood will miss a semester if this is not resolved. Please advise. Thank you.