The story is not true, but try telling that to the BBC.
When the B-52 hit the ice at 450 knots, all four weapons high explosive content detonated, spreading plutonium and scattering debris in a 1 by 3 mile path. Material that wasn't consumed immediately in the fire was later recovered on the sea ice (four reservoirs, one complete secondary, bits and pieces to make up two secondaries). Material that was frozen into the ice and not recovered later fell to the seafloor when the ice melted a few months later. Parts of the B-52 and weapon components also settled on the seabed immediately after the initial impact (the sea ice froze soon after, temperature was about -40 F).
Underwater searches recovered parts of the fourth weapon in the area charted on the seabed (which also matched that on the sea ice). Components included a cable fairing, polar cap, and a 3 by 1 foot section of the warhead casing (other components are listed, but nomenclature deleted in declassified documents). Much of the material is detailed in the sanitized document "USAF Nuclear Safety", 1 July 1968, and declassified letters from the U.S. Department of Energy which were released in 1988 and 1991.
Also, BBC claim of "obtaining" a video of the cleanup is absurd, since the tape has been declassified and available from DOE Historical Films since July 1997.
Technical details of the crash and weapon recovery are available in the book I co-wrote with Jim Oskins-
"Broken Arrow, The Declassified History of U.S. Nuclear Weapons Accidents"
http://www.amazon.de/s/ref=nb_ss_w?_...words=maggelet
Review here-
http://www.amazon.com/Broken-Arrow-D...6493259&sr=8-7
Bottom line- there is no missing nuclear weapon.
Yours, Mike