Help me please, not sure what to do?

I came home and my laptop was on and some programs were open. My uncle and aunt and their family are staying over at my house and I am not sure what they did. I found all of my computers on, one which isnt even working properly. I tried to access my school work from Macintosh HD>James xxxxx>Schoolwork but for some reason everything is deleted. The only thing there on the sidebar is Macintosh HD and Network. I lost movies, pictures, my house, and i am SO angry right now. I don't know how to get them back and I can't believe they went fiddling with my stuff. Nice houseguests they are... can someone please help me get my items back in the Macintosh HD sidebar? Thanks - James.

 

Thanks I found all the files, but i went to finder, preferences, sidebar and they are all checked but when I go to MAC HD and opens all there is is jujust Mac HD nd Network. But if i open like Trash, all my sidebar icons are still there?

 

Nono, they are on the side of the trash... the sidebar. I tried dragging the icon from the trash sidebar to the MacHD sidebar and it just did the vanish thing, what the hell? how do i make them reappear.

 

haha, yes a good idea indeed. I now have the password login on , and this laptop will be locked in my room for the rest of their stay.