solipsistic shit
The solipsistic shit (or solipshit) is the shit you know you've taken, but when you check the bowl, there's nothing in there. This actually has a logical explanation. 9 times out of 10 when this occurs, the shit you took was so powerful and so heavy, that you basically dropped an anchor in the bitch, and the shit sunk to the bottom of the toilet half way down the drain and you just didn't see it.
Person 1: Man, I just this massive shit and I know I did, but there was nothing in the toilet when I looked.
Person 2: Looks like you've experienced the solipsistic shit.