If you know what city he is in, there are probably only a handful of hospitals.
If he is missing already for three days, I think you need to file a police report. In the meantime, call and check with the nearest hospitals around your area.
There is also the possibility that he's walked out on you. Sorry. But that is a possibility, although I hope it's not. Either way, file that police report.
Other people asked questions on similar topics, check out the answers they received:
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them