You are using Spanish locale according to the screenshot. Do you use the same locale for OS (Windows or Mac) and InDesign CS6? Please open  <InDesignInstallFolder>/Configuration/XManConfig.xml, you will find the value for "PreExtensionFolder" (the locale might be es_ES for you.).

<Data key="PreExtensionFolder">$SharedCommonDataFolder/Adobe/InDesign/Versi on 8.0/en_US/Extensions</Data>

Then check whether the folder above exists in your machine. ($SharedCommonDataFolder stands for "C:\ProgramData" on Windows, and "/Library/Application Support" on Mac.)

If "PreExtensionFolder" exists but there is only "REMOVED" subfolder in it, please move all files in REMOVED subfolder up a level to "PreExtensionFolder", then restart Extension Manager; If "PreExtensionFolder" is not the same as that in XManConfig.xml (e.g. Actual folder is ".../es_ES/..." but ".../en_US/..." is specified in XManConfig.xml.), modify and save XManConfig.xml then restart Extension Manager.

All pre-installed InDesign extensions will be put to PreExtensionFolder when you install InDesign. During launch Extension Manager will search extensions in this folder and import them. Extensions will be moved into REMOVED subfolder if they are imported successfully to avoid repeated import, which is what you see in CS5.5.

If both PreExtensionFolder and REMOVED subfolder are empty, you can check whether these files exist in "C:\ProgramData\Adobe\Extension Manager CS7\EM Store\InDesign CS6". If they don't exist either, then they cannot be recovered.

It's strange that every files were in the REMOVED subfolder but no extensions are listed. But you don't have to worry about it if there is no need for you to disable them. All pre-installed extensions take effect in InDesign no matter they are listed in Extension Manager or not. Extension Manager imports them only in order that user can disable/enable them as necessary.