Was your ship count maxed at the fleet cap when you came back for the Legion?
I changed the fleet cap so it was less awkward playing with hobo junkfleets.
> "maxShipsInFleet":50, #30
Doesn't appear to affect salvaging in general up to the new limit, but that Legion definitely allowed me to attempt recovery the first time but not the second.
(And not all of the Legion XIVs appear to be recoverable anyway, as some go directly to scrap upon investigation like any other derelict.)
I don't have that save any more, and I don't have any Legions sighted in my current game.
I will try and see if I can duplicate this when I find one.
[e]
Just tested this and could not reproduce the issue regardless of fleet number/cap settings.
I'm quite happy to be wrong.