Stealing without hostility

I'm incapable of leaving a locked chest behind. I'm too curious.

But I hate losing rep and turning NPCs hostile.

I thought I'd figured out the solution. Using a cleric with sanctuary to loot chests. But the Flaming Fist Enforcers at the Friendly Arms Inn saw right through the spell! Can they see through all concealing spells?

Are there any alternatives? I considered charm, sleep etc. but they all turn the NPC hostile. And no stealth method seemed superior to Sanctuary.

Can anyone advise me on the best alternative?