I’m not sure exactly what you’re saying but you certainly don’t need to drill out rivets to get to it.
I assume you’re talking about the sensor at the start of the tube. Assembly of that one is step 7.19 through 7.21, and attaching the body panel on that side is step 7.40 (maybe look back as early as 7.35 for the prep work).
You might also try talking to Prusa support.