LostSoul
Adventurer
I think it's a choice that depends wholly on the style of the game. In a certain type of game, if I had just pissed off an Evil Empire, I'd make sure no one was coming to get me in my sleep (Divination: "Can we rest here safely tonight?"), and even if I felt safe I'd lock myself in the room. So they did have a way of stopping the (inevitable) attack.
That said, it's possible the players don't know that is the type of game they're playing. I bet they do now. (It didn't cost much to get that knowledge, either.)
As far as locating the assassin, how about Speak with Animals? Maybe there are some birds or small animals around who saw the assassin, and which way he was moving. Locate Object might work if you get it off soon enough (looking for muskets, assuming the Ogre Mage doesn't have any).
I can't think of any clues he might leave other than the gunpowder where he fired off his gun. Not that you could track him by that, anyway.
That said, it's possible the players don't know that is the type of game they're playing. I bet they do now. (It didn't cost much to get that knowledge, either.)
As far as locating the assassin, how about Speak with Animals? Maybe there are some birds or small animals around who saw the assassin, and which way he was moving. Locate Object might work if you get it off soon enough (looking for muskets, assuming the Ogre Mage doesn't have any).
I can't think of any clues he might leave other than the gunpowder where he fired off his gun. Not that you could track him by that, anyway.