I accidently sold The Sapphire Dragon Claw to someone. I Believe it was Belethor in Whiterun, as he is one of the few vendors who will buy nearly anything, and the one I usually sell to. I also remember selling several Dragon Claws to him, though I do not know which ones exactly. I have read that even though merchants restock, the Dragon Claw you have sold to them will stay in their inventory. I was wondering if this is true so I can buy it back from him, as I need it for further investigation of Shroud Hearth Barrow.
According from this wikia page (maybe you already read it) it is possible to buy it back from the merchant you sold the claw. The only way to get it back is to find every merchant in Skyrim and search for the claw.
For PC, use console command:
player.additem <000663D7 > <1>