In short, Origin used to have a feature that let developers provide downloadable extras with their games. But it's planned to be discontinued on June 13th.
The 3rd-party stuff is basically lost if you can't contact support, But EA's own games now have their own dedicated site where you can download said content. Regardless of if you previously owned said games or not.
Alongside the soundtracks. The other free extras include numerous wallpapers, a couple of art books, and the excellent "Final Hours of" Mass Effect 3 and Titanfall ebooks written by the legendary Geoff Keighley. (You might also want to check out his original articles on Command & Conquer: Tiberian Sun and Command & Conquer: Generals , which are some of his earliest gaming journalism work.)