Toilet Paper In The Toilet

Sometimes, when I come home and use the bathroom, I see one, maybe two pieces of toilet paper floating in the toilet bowl.  Sometimes the water in there is white, and sometimes it is yellow-ish.  My working theory: Father blows his nose with the toilet paper and throws it in the toilet without flushing; peeing is optional.

Bothers the hell out of me.  I don't care if it's just toilet paper; that's gross, and I have no bleepin' idea why or how he can't just flush the damn thing.  But that I have seen it so often in my life ... why?  I mean, can't he just blow his nose and throw it in the trash, like I and normal people do?  Instead I see this garbage from time to time when I need to pee, and it sickens me and pisses me off.  I should confront my parents about this.