This will be an exercise in futility and waste the precious little time you will have to respond to the RFE. If USCIS does not have it, that means it either got lost in the transfer from CBP to USCIS or USCIS placed it with the wrong A-File. Regardless, if you get an RFE, I would strongly recommend calling to make an appointment at a Civil Surgeon's office immediately. Bring a copy of the DS-3025 and proof of the Polio vaccine to the CS office so they can transcribe the vaccines to the I-693