Do you know what program or how they were transmitting this webcam stream to each other ? If it was via MSN i doubt that the video is stored unless it has been recoreded using a screen capture software.
So short answer probably not. Although if it was via MSN and you have access to the account, and you know the contact in question you could try viewing a message log by right clicking the contact, go to view then go to message history. It might not be automatically saved though