I have not undone anything; and when I saved and looked at the French translations they were there.
It looks like it was a bug LATER in the Translate tool.

2014-09-27 11:23 GMT+02:00 Guillaume Paumier <gpaumier@wikimedia.org>:
Hello,

On Fri, Sep 26, 2014 at 12:26 PM, Philippe Verdy <verdy_p@wanadoo.fr> wrote:
> French done. I saw you had forgotten a tvar for the video link but visibly
> you saw it too and corrected it the same way I did within the same few
> seconds and saving my edit produced no diff

It seems your edit was saved and it removed all the existing
translation markers:
https://meta.wikimedia.org/w/index.php?diff=10009782

When you marked the page for translation again, it added entirely new
translation markers and undid all the existing translations done
before that. See the example of the French translation:
https://meta.wikimedia.org/w/index.php?diff=10009818

Everyone: The text of the newsletter is now final. There will be no
more changes; you can translate safely. No changes have been made
since yesterday, so depending on when you translated the text, you may
not even have anything left to translate :)

--
Guillaume Paumier