Hi Lucie! I know it's very frustrating, I spend 2 days working on something and lost it with just 2 clicks. I did search everywhere for hours yesterday. Some people say you can look for a temporary file it suppose to start with ps_ and end .tmp
You can rename tmp to tif and get the file back, but the psd layers will be merged. Others suggested to use a recovery software, I did get the file back, same name, same size but it won't open. Giving me some error like "not compatible with this version" like if you try to load brushes to an older version of photoshop.

So I guess there is no way to get the file back, photoshop already take a lot of space with their scratch files, could at least keep the files there until photoshop is closed or have some sort of history even after the file is closed.  Maybe sometime in future.