My sick cat is hiding, getting wet, and won't eat. What's wrong?

Sometimes a cat will hide in an unusual location simply because they are not feeling well. He may feel that getting wet is worth it if he feels safer in the bathroom. Given that he has been sick for a few days and he is not eating, I would recommend that you have him seen by a veterinarian. Cats that don't eat for even more than a few days can become quite ill very quickly. In the meantime, I would try to keep him as dry as possible. Perhaps provide a box or bed in the bathroom to see if he would use it rather than the area that he is getting wet in