I can't complet this mission! It's driving me mad! I need to pickpocket a note from a vampire in the Riften keep. He just walks around in the dinning hall with 3 guards watching him. Never going to sleep or anything. I've tried using the Shadow Stone but he can still see me. I'm a light armor, two-hand warrior so sneak and pickpocket are useless. Any ideas how I can do this mission without murdering him in front of everyone?

If you have low sneak just forget about it

So I just murder him in front of everyone?

Or do the quest later, unless you can't.

Yeah, I had low sneak so you should just wait and focus on leveling up your sneak skill.
Or you can just kill him and be done with it.

I finished it. It took about 50 tries but I got it.