Guards can see through walls, unfortunately.
I walked up a flight of steps to a door in a dungeon getting ready to open the door when I was hit with a bolt of lightning, arm through the locked door and I was zapped.
But the stealing thing is a joke , I was upstairs in an Inn , outside my room was a table with some apples on it and a book. I press E to read the book but took an apple by mistake, I heard all this shouting down stairs and swords being drawn then footsteps thumping up the stairs. I went down to see what all the fuss was about , met a guard on the stairs, right your coming with me .. WHAT !
Didn't know they had CCTV upstairs in the INN ...
Guy that "killed" his Mrs and wee girl , done the mission killed a load vamps and the guy as well ... Well done I was told by the Jarl and here is a reward .... I went back to this house , family all dead and buried but still put my cursor over anything and it has the Red STEAL on it.
Another one , on my way from one town to another I seen a merchant being robbed , two of them were fighting robber killed the merchant but must have been badly wounded as the merchants horse reared up and killed the robber. Both dead but when I went to take the dead merchants horse I put my cursor on it and it asks if I want to Steal it , its owner was dead!