I don't know what the Board of Pharmacy requirements are for various states, but they can't be that different from mine. In my state, a prescription is only valid if the prescriber's information is clearly on the prescription, including name, address, phone number, etc.
You'd be surprised, though, how many prescriptions we get from discharged patients with incomplete information. Missing names, missing instructions, one doctor listed on the top of the Rx and signed by someone else, no phone number... it goes on and on. And EVERY time, we have to call the hospital to get the rest of the information, and that usually involves 2-3 phone calls to eventually reach someone who can answer the question. And 90% of the time this occurs during a busy time in the pharmacy and the patient's representative has the actual patient waiting in the car in the parking lot and are always in a hurry to get the patient home (perhaps they should have taken the patient home first, but that's another story). So there we are unable to fill the prescription right away. In some cases, I've had to give back a prescription because it's not legal and I can't fill it.
PLEASE, PLEASE, PLEASE, I implore you... if you're a prescriber in a hospital and you're writing scripts for your discharging patients, PLEASE take a few moments to fill them out correctly. Give us some idea who you are. A scribble doesn't do it. If it's a controlled substance, PRINT your name and put your DEA # on it. We're outside the hospital, not the hospital pharmacy. We don't know you're particular scribble. We can't read your mind. Please fill out the prescription completely so we don't have to track you down or bother your nurses to find out what the hell you're prescribing or who you are. Don't do this for us, do it for YOUR patients! They're out in the parking lot and they really want to go home.