cant find 4 digit code for immobiliser?

hi my immobiliser packed up 2 weeks ago when it was really cold. can use key fob for central locking just wont turn immobiliser off to be able to start the car. been to renault for 4 digit code and when they put it in there computer they said there are no longer any codes for the car because of its age ????????? common fault on renaults of that age apparently so thought the dealers would still have codes?????
my vin no ( is it the same as chassis no??) if so
VF1JA0FL519482000.
i have an 8 digit immobiliser code which renault did give me, 57255275.
hope u can help me .xx