I just want to know if it is possible that Pickpocket fails and I still get away without a penalty?
Because when I do it on sleeping people - it is dark in the room and even when they awake, they should not know who I am as long as I get away quick enough. Same with drunken people, but maybe not when it happens at daylight where everyone can see you.
Well, from my experience, even if you run away from a sleeper that spotted you, he can eventually tell it to the guards. Later down the road, you can get a perk so people who like you can close an eye when you unsuccessfully pickpocket them. At least I think. Check the pickpocket perks 
Yeah, but for me it doesn’t make sense that you pickpocket at night when you still can’t run away… and the perk says that if people that like you see you pick pocking, they won’t scream, but lose faction points as well.