Isn't the chassis number on the driver's door jam. IIRC I have a sticker there also a sticker of when my SRS/Airbags were upgraded in 2007.
That's the VIN, but you can use that # on the VIN Decoder to get the chassis # :thumbsup:
You don't say where you're located but it sounds to me like you're looking at the small metal plate screwed tothe radiator support. That plate does not include the chassis number, at least on US market cars. That's where the codes for options installed are.
Look at the bulkhead ahead of the battery for the chassis number: