[ubuntu] Very Strange Thing

Hello, i would like to ask you about a thing which is related to Ubuntu's security.

I have been using ubuntu for a long time but i has never happend to me before the thing is:

2 days ago when i was programming i left my room for a while and when i came back , the window i had opened (IDE) was closed (minimized) , i was impressed how could it happend when i was sure i left it oppened , later on i started to be nervous because i still didnot get how could it get closed , i started to think about that someone has gained remote access to my computer and it would hurt me alot , i started to google all the things how to check whether someone has coected to my pc etc.. i didnot find anything suspicious i used sudo last and commands like this , but i still couldnot remove this idea from my mind i still analyzed it etc , i didnot have SERVER on my pc and i didnot allow the SSH to run , i also didnot install software like team viewer i have read that there are still some ways to gain the remote access but i am sure i didnot install anything that could harm my pc , i had just Sublime text installed and some basic official programs like Code Blocks and Wine nothing else , i still couldnot solve this , but i finally realized that the best thing to make myself sure is to reinstall the system (yes maybe im a bit paranoid) so i reinstalled to ubuntu gnome http://www.ubuntugnome.org/ i chosed : erase disk and install ubuntu gnome everything was fine untill the exactly same thing happend today , exactly the same thing , so i wanted to make sure whether the ubuntu might sometimes close (minimize) the windows unexpectedly or so , or is it possible that someone has infected my "harddrive" in the past without my knowledge and even if i reinstall the system and erase the disk the virus is still binded to hardware and it allows someone to coect to my system ? haha this is very strange and i dont believe it but i just wanted to share this , can someon explain me what is this ? how could this happen? or even if it could happen? maybe i was very tired but i cant sleep because of this. thanks

i cant even image that someone would gain the remote access to my computer , to all my files and would copy them or so so this is why i solve it that much