They sent him back without conducting the interview?
I was sent back on my third interview appointment. I showed up and the clerk said my file had not coem yet.
My previous two appointment was cancelled and I received cancel letter in advance. But I did not received such
letter for my third interview appoinment.
But on my third appolintment it is nice of the clerk to tell me that he would make personal inquiry into the matter
and promised he would called in that week. It was monday. On Thursday he did call med and told me my file arrived
and ask if I could come next week. This endded my sceduled-de-schedule perpitual loop and everythoing from then on
became a happy expeirence even I had a complicated matter in my case.
But for OP, I think it is USCIS that get something lost and they are trying to locate it. So the OP does not need to send
anything now but wait.
I kind of supect my a file not arriving in time had something to do with my FIOA request. My FIOA request
was complated before the inetrview though I received it after my naturalization. It was a CD. Inside CD
contained everything I sent to USCIS/INS before including N-400.