Is it bad behavior of an employee to call out sick 3 hours before a shift?

It would have been better if you called in at least 6 hours to a day before hand, because the boss had to take your problem into his own hands, which cost him his own time. It's not awful, but it's definitely not polite. You should be fine, apologize to him for putting the problem onto him, and offer to cover a couple of his shifts for the next few weeks.