Correct, scrap aluminium (especially the higher grade aircraft component alloys) are a traded commodity, carried as bulk cargo on large vessels.
Well, all the (valuable) aluminum items are missing, so they may have been removed. What was washed ashore is the remaining composites, which can not be recycled and is much cheaper to dump somewhere in a thirld world country...
There should be quite some 777 flaperons slowly rotting somewhere on this planet by now. There is still no use for old CFRP composites, and no way to recycle it.
However, the french should have some strong indication by now at which time this flaperon has been produced, and if none has ever been scapped of that batch, bingo!