It would be a good idea to have a buyback section in the markets where you can get the item back for the gold you sold it for. This could reset itself daily as well. This is useful for those people who sell something, thinking they have no use for it but later find that they really should've kept it. Frankly sometimes people goof up and sell the wrong thing and all of a sudden that rare item you accidentally sold for chump change now requires a significant amount of your savings to retrieve. This will fix that issue nicely.
I have more problem accidentally dragging my equipment over to the shop area instead of inventory area. The ability to buyback sold item with the selling price as long as you stay in the shop would be a nice addition.
I made a thread about it. A sub-topic was buyback. apparently it's on Jons to-do list http://www.cardhunter.com/forum/threads/suggestion-oh-no-i-sold-my-phat-lewt-and-epix-again.2444/ <- original thread