I've got the scripts for both movies, and the missing reel was written into Planet Terror. The lapdance scene was in the script for DeathProof though.
That was probably why the missing reel in Death Proof seemed so strained. I know it was a staple of Grindhouse films that when they were showing these films an entire reel would be missing but for Planet Terror it seemed a natural part, while Death Proof just didn't pull it off.