Rationale for PO Vicodin in ED?

I will be starting nursing school in the fall, and in the meantime, I am a volunteer in my local ED. We had a patient who presented with an ankle fracture that he had been walking on for several days. Of course, it was markedly swollen, and there were large, but thankfully unpopped fracture blisters. He appeared to be a chronic alcoholic, and it is possible he was intoxicated at the time. It wasn't on the board, and I didn't smell alcohol (didn't snuggle, though), but he had heavy eyelids and was slightly unfocused, slurred speech. I know when you drink for long enough, you start to act like this even when sober.
Anyway, when I went in to check on him, he asked if he could have another Vicodin, even though he wasn't supposed to get one for another 10 minutes, because the pain was real bad. He was really calm about it (I would have been a huge baby!) I told the nurse, who ended up having to wait another 1/2 hour, because the doc went in and poked around.
My question is, what is the possible rationale for giving PO Vicodin instead of IV pain meds for an obvious "objective" injury? I would think even a nerve block of some kind would be more humane. I wanted to ask but I was too chicken because the nurses are all so busy. Any opinions?

~Mel'