Probably just something in the food you ate or something that fell in the toilet.
It's possible:
The spiny projections along the edge -
INTESTINAL parasites (Helminths)
TREMATODA Order: Echinostomata
There are several parasites in this group
most of these are smaller that your object.
Another fluke, Fasciola gigantium, is quite large, see images if it has bristles.