Yeah, I just learned the hard way what you're going through. It's some kinda stupid bug!
Like any seasoned gamer, you save just after you win a fight right? Trouble with this game is if you save before you've fully completed this scene, you'll get stuck with this bug.
You have to start over from unlocking the bedroom door and luring the guy into the bathroom all over again.
if you haven't got a save point from before locking the guy in the bathroom, I think you should be able to unlock the bathroom, go in, he'll attack you, get a "game over" then you'll be returned to the bedroom and the guy's back in the kitchen.
When you've successfully got the guy locked in the bathroom he should start complaining. Then you can exit the villa and you'll automatically run into the cop. Once she takes over and leaves you, you'll be outside the villa near the dog, THEN that scene is completed and you can save.
This bit wouldn't have been so bad if the point and click mechanics of the game weren't so slow and vague.
I don't know how many times I had to replay this because I couldn't get the key out of inventory and onto the door properly.