Confidence Poo + Ghost Poo = Perfect Poo.
The situation chronologically would work as follows: Person sits on toilet to take a dump.
When bowel movement complete the person is confident that they dont need to wipe at all. Person then stands up, pulls pants up (thus completing a Confidence Poo) and observes the bowl only to see no trace of the poo whatsoever (thus completing a Ghost Poo)
This remarkable feat is only rumoured to have occured and no primary sources tell of its tale.