I'm an RPH/Clinical Coordinator for my hospital & it's definitely true. The thing is you see a lot of drug dealers, rappers & addicts with that drug but they aren't getting their supplies from hospitals. We have prometh/codeine in our narc vault but it's very rare that we even give that out to a inpatient.
Those stolen bottles are coming from retail pharmacies only. Usually one PIC(pharmacist in charge) is responsible for ordering products that are called "fast movers". So retail rph's will order 20 bottles but only 10 will end up making to their store & the other 10 will be sold for a high street value.
Also prometh/codeine is a CV drug. Yes it's still a narcotic but the DEA only gets suspicious of CII & CIII drugs which are morphine, methadone, oxycodone etc..
Another drug that stolen a lot is Diprivan(propofol), it's the same drug that led to the death of Michael Jackson. It's a sleeping anesthesia analgesic but a lot of people in hospitals have been stealing it & selling so nationwide all hospital pharmacies cracked down & now treat it like a CIII narcotic.