Hi I wouldn't suggest hay in the litter box, as he would have that for eating and they like to eat and pee in separate places. Rabbits are very clean and choose to pee and poop in one area. Try and put a different substance in the litter box and if you find pee then scoop some up and put it in...
I have a neutured male Netherlands dwarf sharing with my female lop which is spayed, every time a female rabbit goes near the hutch my lop will attack my Netherlands dwarf, why? Then if a male goes near the hutch my dwarf attacks my lop...help ?