Oh yes it is possible and common when you purchase any Gift Card at a retail location where they display those cards on a rack where the public is free to tamper with them. You were scammed right inside the store and Target failed to protect your purchase. The scam has gone on for years where someone grabs a bunch of cards off the rack and then carefully opens the package to scratch/peel the sticker and write down the code. They can also further scratch the code to give them more time to use or sell the card.
Once they have the code, they put a new sticker on there that can be purchased at Amazon and place the cards back on the rack. Now all they do is sit back and wait for you to pick up the card and take it through the register to activate it. Once that is done, they can sell it on a third party website where it will be redeemed.
Ironically some of these same retailers will lock up products that are stolen from them resulting in a loss of money, but don't have the same concern for their customers who lose money by their actions to not secure the cards. Only purchase Gift Cards from retailers who sell them securely behind a counter or purchase them directly from Apple.
As for getting your money back, I have seen reports where users were able to escalate the matter with the Store Manager, District Manager, and the Corporate Office of the retailer. The store is well aware of this scam and is no surprise to them, yet they fail to do anything about it. It is even reported heavily by News outlets every year over the holidays when Gift Card purchases are common, but of course it can happen any time of the year.
