Recently, the Unity "Files & Folders" lens can not find anything I am searching for using the dash.

Let's give an example :
I want to find a document called "Figure_1.png". Before this trouble, I could write "Fig" in the dash and all the documents starting whose name would contain "Fig" will be displayed in the results.

Since, yesterday, nothing happens and I just got the three types "Recent", "Download" and "Favorite Folders" populated. Even if the document "Figure_1.png" is present in the "Recent" subcategorie, typing "Fig" wouldn't only restrict the result to this document.
It seems that the search motor has been killed somehow.

All other lenses behave as expected.

I tried to reinstall the unity-places-files application as well as zeitgeist and log-in/log-out without success.

Also, when I run the command zeitgeist-daemon --replace in a terminal, this error message appears :

ERROR - zeitgeist.extension - Failed loading the 'SearchEngineExtension' extension

I don't know if that might be related to my problem.

Do you know a way to get back this very important feature ?

Thanks for your answers.