Assuming UK?
If you failed then you must have had a couple of faults - just one minor fault and you would have had a partial pass where you only have to retake the section you failed rather than the whole test.
I thought if someone failed, you were recommended to undergo further training and I'm surprised the CAA could rebook your test in two days.
What does your school and instructor say about appealing? They are the ones who should be supporting you on this.
Cheers
Whirls