If you got the gift, it would appear in your purchase history at the Sims 3 Store and would be labeled as "Gifted item from [username]." Are you logging into the right account at the Sims 3 Store (if you have more than one account)?
If you are logging into the right account, are you sure you were given that gift? You said "I at one time thought..." as if this happened a long time ago and you're not sure. I say that because I don't think it's possible for the Store to erase something acquired through the store. It works like a shopping cart. Once you are gifted/buy an item, it becomes logged as part of your purchase history.
