ATTENTION! Please note that even if the date code is legit, this doesn't guarantee that the item is authentic.
Here's what might be the explanation:
1) Your item is vintage and was manufactured before 1980
2) The code was stamped into lining and worn off. It is very typical for alcantra lining. Looks at the examples below - it's barely visible.
Where can I find my bag's date code?
Louis Vuitton Date codes are always located on the different parts of the bag. The most typical but not exclusive can be pockets (next to the sewing). The date code can be stamped on a leather tag inside, to the lining or to the vachetta (white leather) parts.
Keep in mind that the fact that an item has a date code does not guarantee that it's authentic since many counterfeit items also have valid date codes. A valid and properly stamped date code is just one of many parameters that are checked to guarantee the authenticity of a Louis Vuitton handbag.