During the Theives Guild quests there are trinkets you can find that can be sold to Devlin for a high price. Not sure if there is a reward for getting all of them but this is the only one I missed as like you I only found out they are useful after I'd done a few of the quests. --- Smoke me a kipper, I'll be back for breakfast!
Hmm... have you tried just going back to the location and stealing it? It was near the entrance so it shouldn't take long. I've no idea if it'll result in a bounty or not though. --- It is only with the heart that one can see rightly; what is essential is invisible to the eye.
Hmmm, I reloaded and sold the statue then went back for the map. When I steal it I don't get the pop up to sell it to delvin and he has no option for me to sell it to him --- Smoke me a kipper, I'll be back for breakfast!