"Over the North Sea" probably doesn't quite summarize their position. They were supposedly flying along the coast, well within gliding distance of land, when they disappeared.
I was actually flying quite close to that area at the time. There was a significant amount of sea fog drifting in. Various aircraft were turning back from the coast one way or another. I was maybe 8 miles inland in severe CAVOK conditions, doing aerobatics up to FL50.
I heard ATC trying to contact the plane, but didn't hear anything about them being missed until I got home. Not that I could have made a difference - I wouldn't have gone into that fog anyway to help locate them.