Earlier quoted context omitted.
To elaborate, it appears that American English treats "hospital" as a place. So you go to the hospital, just like you go to the airport, or the subway station. On the other hand, Commonwealth English treats "hospital" as something more like a state. You go to hospital just like you go to work.
That's a good way to think about it. I couldn't think of a rule for when I drop the article. I guess for the state in the US we would say "hospitalized". So I would say "he was hospitalized", unless the identity of "they" in the original quote was important.
I know online dictionaries say both are correct, but irregardless[1] it's one of those words that really irritates me.
--
[1] Yes, using that word is an attempt at written humour.