A quick trip to the vet confirmed the suspicion. Bootsie got lots of medication and would soon be well. His owner was relieved to know that Bootsie's behavior was caused by a physical problem. Everything would get back to normal once the medication did its job. After his visit to the vet, Bootsie used the box again.
Antibiotics take a few days to start working so the return to the box was still painful.
Bootsie was further convinced that the box caused the pain. He continued his quest to find painless place to eliminate. As the medication started to take effect, Bootsie's discomfort decreased. Each time he urinated outside the box, his behavior was reinforced. With perfect feline logic he was now completely convinced that he could avoid the pain by avoiding the box.