All of the sudden without doing anything I know of my whole download folder is empty!?

So this morning was on my macbook pro running yosemite 10.10.1 and all of the sudden I see that my download folder is completely empty... And there is nothing i can find in my trash bin? It's so weird. I have always been a windows user so I have no clue what might be the cause of this. I did download a "suspicious" file called mac keeper... I did this by accident I was looking for something else. I didn't install it or what so ever I opened it and canceled the installation. I'm not sure if my files were still there before that...

Could anyone help me out here to prevent this from happening in the future... all my other files are okay so I really do not understand what happened.