Well, first off stealing shouldnt happen its not lawful, also most stores have the codes deactivated until bought at the register and then they are active. The code might not work. For example, you want to buy a Visa Gift Card so you can buy some stuff off of ebay and you have no money so you take it home without paying, it will not work because most codes on items like cards or games are fake UNTIL bought and activated by the cashier of the register.
P.S : Never steal, EVER, it will come back to bite you in the butt.
P.S.S : I never stole anything .....