Just keep telling that nagging voice to shut the hell up until it actually does. Having my mother be a full-blown alcoholic for nearly nine years, I can tell you that even living with your father and being around him all day long wouldn't be enough to keep him from drinking and doing something stupid. When he gets the urge to drink, nothing short of locking him in a closet is going to stop him from finding a way to do so.

tl;dr don't beat yourself up over it, your dad is an idiot.