As I got back to my computer, I saw the Teamviewer alert dialog that says :
"This was a free session sponsored by www.teamviewer.com"
This probably means that someone connected to my computer and ended the session.
How can I search in the Log to know when and how long this session was? And also who connected.
This is quite worrying because the Teamviewer ID is just a sequence of numbers, and the passwords are really short.