i saw something on discovery channel about this stuff a long time ago.
one story claimed that a bomber had trouble just outside of New Orleans (i think) and either crashed or jettisoned the nukes it was carrying (i cant recall which)
reports claim that just outside a coastal city (cant recall which) there is a nuclear war head probably buried in 10 feet of sediment.
other reports claim that the warhead was probably destroyed.
either way it was not recovered.
it was an interesting show.
EDIT: found it... Savanna, Georgia