Citizenship Interview- File lost by office

My mother filed for N400 for US citizenship but on the day of the citizenship interview in California local office, the officer informed my mother that they had lost or could not find her file and she had informed her supervisor and they will ask for the file again and she will be contacted later for rescheduling the interview.

Does anyone has experience with this as now 1800 number they gave are saying processing time is 12 months and contact us if case is not processed till then. How long would it take to reschedule or hear back from them as the online status is still the same and no updates. Its been a month.
 
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