Dear Karine,
The Dorothy Gibson film, which I think you are referring to, is most assuredly a lost film. It has been mentioned often among film historians as one of the most sought-after, but as yet undiscovered, early silent films - and in at least one book on movie history there is a chapter on the film. I do not recall the title.
You must remember that, according to the American Film Institute, nearly 70% of all films pre-1930 are lost - "lost" meaning that they have been destroyed by old studios or else have deteriorated over the years in film archive vaults due to the nitrate they were made of.
The German 1912 film, "In Naucht und Eis" ("Of Night and Ice"?) does survive but has not been released commercially as, I imagine (since it was recently discovered), it is still being conserved by whatever archive now has it.
Inger Sheil did not specify in her post under the other thread but I would think the friend of hers who viewed this was looking at a specially-requested private viewing tape which researchers have access to (though often for outrageously high prices) in most film libraries/archives.
I hope this helps to clear up for you that, indeed, "Saved From the Titanic," released by Eclair Films in May 1912 and starring Dorothy Gibson, is sadly currently considered lost.
All the best,
Randy
Randy