I had a B file for a while , my initial application was denied , took us over a year to get the appeal approved. after appeal was approved , file went back to the embassy to be re-process outside of Canada , thats when the file changed from a B file to and F file. apparently im not alone getting files number that start with an F. i read somewhere that once the file get denied and you go to thru the appeal process , the file will disappear from ECAS. and then it will be available to review with the new file number.New Wife said:I talked to immigration here in Canada today and they told me that the "F" number is not something that Canada uses. It would be unique to what ever embassy you are dealing with. Your "B" number should still be active and in use. If you think you are having problems, or anyone, the suggestion was to send a nice polite email to the embassy you are going through and ask them about the "b" number and the problems you have encountered.
the strange part is that the system only recognizes B files and does not recognize the F file. sending an email to the embassy will take about 28 working days to get a response , and usually their response is that they will contact you if they need any additional information.