Hi. I have exactly the same issue, but with a normal sim (not a fairy). My sim has several reward traits that completely remove the need for the toilet and other basic needs. Free will is disabled, ...
Ideas
This is happening to my whole Sim family. Bladder need bar is full, but the toilet thought bubbles pop up around 8 hours for everyone. If I let them pee (although they don't need to), it goes away for several hours (probably 8 but haven't timed it).
