What number are you looking for, VIN? Part no? Type of tranmission, Auto Manual?
What makes you suspect it was tampered with?
In any case, the vehicle VIN number may be on the transmission (usually it is on a metal tag that is secured on the top of the transaxle - same with body panels having a little sticker with the VIN). For a 2004 Corolla with an Automatic transmission - the model number is A246E. Manual transmission - the model is C59.
Also look up you model code - should be on a metal tag under the hood or on the door/door jam area. Would be something like ZZE130 L- DSPDKK or similar. Usually the 10th digit in refers to the type of transmission was installed at the factory. M for 5-speed manual, P for 4-speed auto.