Rob21,
From the article in the New York Times where the author met with the coroner in Brazil who did the autopsies.
The far wall lighted up, and we began viewing images from the autopsies. “We took pictures of everything,” Sarmento said, scrolling through pictures of watches, necklaces, earrings and rings, still clinging to blue-green wrists and necks. “We were able to make all of the identifications.” As the images flashed by, he added: “All the autopsies were observed by the French and by Interpol. Not one country, not one family, complained about the identifications.”
...
He leaned forward in his seat and wrapped his arms around his knees. “They were like this,” he said, holding the crash position and looking into my eyes. Then he sat up quickly and held his hand flat above the table. “When they hit,” he said, slamming it down, “fractures. I believe the pilot tried to land in the water. This is consistent with the fractures. But when the bodies arrived, the lungs were already in a state of decomposition. We didn’t have conditions to see if anyone drowned.”
....
“So it’s possible that some of them were still alive?” I asked.
Sarmento nodded. “Most died on impact,” he said. “Some could have survived.”
....
A few days later, in Paris, I stopped by the office of Alain Bouillard, the lead crash investigator for the B.E.A. After studying thousands of pieces of wreckage, Bouillard came to the same conclusion as Sarmento about the plane’s landing. Many of the items recovered, like meal carts, were found with their contents compressed from the bottom, and pieces of the plane’s underbelly were flattened as if struck from below. “There is a high probability that the aircraft landed in one piece,” Bouillard told me. “We are reasonably certain.”
“The medical examiner also said it’s possible that there could have been survivors,” I said. “Do you think so?”
Bouillard was silent. “I don’t know,” he said. “It’s impossible to say.”
http://www.nytimes.com/2011/05/08/ma...ted=1&_r=1&hpw
I don't think that a body losing clothes would retain a necklace.