The NBC # on the yellow letter is correct, if you call the 800# and use the automative system and enter the #,the system will say that the number is incorrect and that you need 13 digits, what you need to do is call 1800-375-5283 , then press 1 for english,then press 2 to check status of application, then press the # for the option that ask if you lost your receipt #, you will be transfered to represenative, just give them number on the yellow letter NBC*xxxxxxxxx
Or you can use it online at uscis.gov
DO: BROOKLYN, NYC
04/29/2010 (0) : Lewisville Tx
05/02/2010 (3) :N-400 Rec. Dallas,Tx
05/15/2010 (16): NOA Rec.
06/22/2010 (52): Rec. FP letter
07/09/2010 (69): FP Sch & done
07/15/2010 (75):YL Received
08/21/2010 (112): Case sent to local off.
08/23/2010 (114): Interview Letter
09/29/2010 (151): Interview Date / OATH LETTER
10/15/2010 (167): Oath & USC
10/16/2010 (168): Passport Application@post office, (Received 10/20/2010 @ PP Regional Office)
10/30/2010 (x): Passport Received