Ah, I hope he/she comes back. I had a cat that did something similar knowing she was about to get a bath. She returned after a couple days but something about her had changed. For one thing, my mom was afraid to pick her up again. So it was no more baths, but from then on the cat had to stay in the garage at night.
Tigger is an indoor cat. He eventually wandered back into the den and took his meds like a, well, cat. One more pill tonight and we are done (assuming that the ut infection has cleared up).