I've just discovered a similar problem, but it's not just themes. There's a whole bunch of stuff that I can see my purchase receipts for, but the content itself is just gone. Not available to download from my purchase history, doesn't come up if I search for it using the exact title, just *poof* like it never existed! I have always found it frustrating that Samsung locks you into their store to be able to change these things, rather than purchasing items in google play and them then being stored on the device itself. Even if content is removed from the play store entirely, you still retain ownership of it that way. Now I'm wondering how much money I've just poured down the drain on content I've already lost or will lose with future updates!