Make sure you're in the right Saved Games folder, and that Liberation is configured to put the generated mission into the correct Saved Games folder. It should be the Saved Games folder in your user directory.
For example, I have my user directory moved off of my C drive to my D drive:
My user directory is at `D:\username`, but the default Windows location is `C:\users\username\`. This means that my Windows profile folders (Documents, Desktop, Downloads, Pictures, Saved Games, etc.) are not at the default Windows location. (I did this when setting up my PC by [Shift+Right-click]ing each folder, selecting Properties, and selecting the Location tab.)
The default location of `C:\users\username\Saved Games\DCS\Liberation` exists because Liberation improperly creates that folder instead of pulling my proper user directory location (so it should be `D:\username\Saved Games\DCS\Liberation` if Liberation did things properly). It simply assumes you have the default locations for everything, and then creates it if those folders don't exist. It also defaults to assuming your DCS Saved Games directory is in the default location alongside of itself.
DCS itself properly uses my `D:\username\Saved Games\DCS`, as it should. That's where I moved my Windows profile directory to, after all! Liberation doesn't find this directory by default, however; I have to tell it where to go, which is annoying.
You can see in the attached image what each directory looks like on my PC.
# TL;DR #
What I suspect is happening is that DCS is using a different Saved Games directory than what Liberation is configured to use. You can which directory Liberation uses by opening Liberation and selecting File -> Preferences.
Try going there, selecting the `Browse` button next to "DCS saved game directory". Then, in the *TOP* of the file browser (not the bottom) enter %USERPROFILE% and press Enter (the percent signs are important, don't cut them out). There should be a `Saved Games` folder in that directory that has a DCS folder inside it. (I have 2, and have to be careful which one I select.) That DCS folder should contain folders such as Config, Data, fxo, InputUserProfiles, Missions, etc. That's the DCS folder you should be selecting.
If you only see a Liberation folder inside of your selected DCS folder, then you're in the wrong place.
(And don't forget to hit `Select folder` and `Apply` instead of just closing the windows!)