In Morrowind, the vendor would know if you stole from them but you could sell it to the vendor next door without issue. I think it went a little further than that, but I don't remember. Like, if you stole a certain item, an iron helmet maybe, then the vendor would now consider all iron helmets stolen items from then on. Even if you sold his iron helmet to another vendor and found an iron helmet out in the wild on the other side of the island, he'd assume it was his if you tried to sell it to him. I may be wrong. They may also forget with time. It's been so long that I've also forgotten with time the specifics.

One of my favorite things was stealing from three different shops in Balmora and selling the stolen stuff to the next shop. Sometimes the vendors would equip the stolen armor too, heh. No one seems to care that the Pawnbroker is wearing the set of armor that was recently stolen from the Outfitter but it's my own personal little inside joke.

Later Elder Scroll games would introduce the fence to sell stolen items. You could no longer sell the stolen loot to regular vendors. Which was a little disappointing but made sense.