When I started playing again at the end of last August, I came across Barnacle Bay: http://store.thesims3.com/barnacleBay.html?categoryId=12642§ion=UpSell and it was a free download. I just assumed at the time that I had bought it previously and due to changing computers, I had lost it somehow. It still doesn't show up on My Page as being owned, though.
ETA: @igazor, that's probably it. One of my games was a Limited Edition; remember getting a thumb drive with a green Plumbob attached. It was before Origin, around 2009/10.
