Will try to post a pic of the only number stamping I could find on the left side trunk lip. I believe the number is 2838511. A similar number, 2838510, is stamped on the passenger side.
You're close to finding it if it's there which I'm betting it is. Go right above the part number stamp and a little forward or to your photo's right (between the white lines) and remove a lot or most of the paint. (you can just see the number 2838511 stamped from underneath on my Y4 A12 photo below my trunk lip number so you're in the right church just in the wrong pew)
