My audio is there but how can I get back my video? This was displaying my video and playing the accompanied audio track.
However somehow I tried moving some windows around, and now I get this, a blank video with perfect audio. 

Is there any way to discover where my video is hiding and synchronize it to the audio once again?
Your preview window is displaying a histogram (technical reference image). Click on the checkerboard icon at the bottom of the VSE timeline