What's even more obvious is that his doctor wouldn't have stopped prescibing the pills if Rush needed them for pain. And if Rush is still experiencing bad pain, why would he stop taking the pills? The story doesn't add up. It's a safe bet that this rehab isn't the least bit voluntary.
Actually, that's not obvious at all, because it's very common for doctors to be quite "paranoid" about prescribing strong painkillers on a long-term basis, and cut off patients who still badly need the medication. In fact, the heavy federal regulations concerning "controlled" medications very strong encourage such things -- doctors can lose their license or go to jail if a panel of bureaucrats thinks they prescribe "too many" controlled painkillers. My wife had acute chronic pain for many years, and we saw this first hand, and have met and read about countless other people experienced the same problem.
The prescription habits of doctors licensed to prescribe controlled painkillers (and most are not) are watched so closely that the prescriptions have to be written on special "triplicate" forms, one copy of which is mailed directly to the government oversight body, which computerizes the information and can easily review it for anything they consider a "red flag".