From the article: 'A friend told BILD that he last heard of him one year ago on Facebook for his birthday.'
That comment may have been about the automatic Facebook "It's Manfred's Birthday" messages, not an actual contact initiated by the deceased. From the looks of Manfred and his boat, he's been dead longer than one year. Other articles mentioned that he hadn't been seen since 2009 (before his wife died).
The letter to his (ex-) wife sounded as though he'd just learned of her death. His Facebook profile photo was updated in September, 2011. That may be the last evidence that he was alive.