Mine has had the same thing happen twice now. I just left it for 5 minutes and the screen saver came on, then when I came back the taskbar was gone.
I managed to fix it by going into 'Taskbar and Start Menu Settings' in the control panel and playing around. I moved it to the other positions around the screen and it still didn't appear, but I got it to come back by selecting 'auto hide the taskbar' and then deselecting it.