I have made a project with video tracks and audio, but somehow I managed to close my source layers for my video tracks. Only my audio tracks are visible. If I play my sequence, the video do play, so they are not gone.
It is probably just a checkbox somewhere, but I cannot find it.
Like Ann says, move you cursor to the little bar under the wrench icon in the Sequence window (circled in red) just above your A1 audio track. You should be able to click, hold, and pull down to reveal the video tracks above.