Death dealer Talent Hidden weapon Damage bonus

The Death dealer Talent states “You are a proficient killer, relying on trickery and misdirection.
When armed with any weapon that has the Hidden Quality, you may substitute Stealth for your Melee and
Ranged Weapons skills, and increase the damage of the weapon by +1§.”

The Hidden attribute on the weapon only comes into play when used from hidden place. as stated “When the weapon is hidden, any search of the owning character requires an Observation test, with a
Difficulty of X, to locate the hidden weapon. Immediately after using this attack, a character may spend Momentum to conceal it quickly, hiding it”

does this mean the bonus damage is only when attacking with the weapon from it hidden place and there after since it is not hidden any more the bonus damage does not count?

Well as written, the Talent states that the weapon only needs to have the Hidden Quality to gain the benefit, not that it needs to be hidden the moment before using it.