That's what I was thinking, and what I think is dumb. Morrowind wasn't like that. You would get caught if you tried to sell a vendor their own stolen item.
Morrowind got it -partially- right. However, one problem with Morrowind's system was that once you stole an item from a merchant, EVERY item of that same type was subsequently (and permanently) marked as owned by that NPC, so say you steal that grand soul gem from that wood elf enchanter in the Balmora Mages Guild. If you stole that from her, brought it to another enchanter to use, then came back with another grand soul gem for HER to enchant your stuff with, she would attack you. It should not be like that in Skyrim. Merchants should be able to tell whether a single item is theirs or not, however on the other side of the coin, an apple should not be known as stolen to a merchant on the other side of the continent as the merchant you stole it from.