deleted entire video layer in my timeline

So everyone knows there's two parts the your timeline the Video layer and the Audio layer, where you control EVERYTHING. So I was editing my film and suddenly my video layer is gone and I just see the audio layer. As one does I look on youtube and youtube has nothing. I reset to previous settings and I went through all the settings, and coulkd not fix it. My movie is due in two days, can someone help me....