Lost folder and session

This will be hard to explain as I have no idea what happened.

I created a new session and did the shoot. After I was going through some of the photos and then CaptureOne crashed, then I wanted to open up the session again and it is gone. No folder anywhere and I can not find any trail from it. I had it saved on my desktop and I think during the session my harddrive got full and it might have crashed because of that. Is there any way to see history or search for it? I tried to do the trick to replace it but as I can not even find the output folder that is not possible.

Thank you for any kind of help.