[Help] Shop problems.

---EDIT---
So I figured out why my shop said it would buy for 0 gp on items in my general store. the shop needs to be labeled 0 for buy, meaning it will buy anything. and 2 means it buys only what it sells. so 1 would mean it buys everything for nothing so i guess we don't use it.
Under buy;
0 = buys everything, 2 = buys only what it sells, 1 = buys everything for nothing.
Under sell;
0 = Sells everything in stock, 2 = Sells only what it has, 1 =Sell only what it has.??

But the shop when you sell an item to it, that item will just disappear and not show up in the show. How would you fix that?
I want the shop to add what ever the players sell to the shops to add to their inventory when they sell it. not have it disappear.
I need someones help please.