I think MM deleted unviewed film.. is this possible?

I was editing part of a tape that had various subjects on it. I created a
couple of movies, saved them, then closed MM. when I went back the next day
to view and edit some other portions of the tape, i discovered the tape was
empty... after the video I had edited and saved, there was nothing left on
the tape. I had the save switch on the tape on, so I do not understand how
the information could have been erased. Is there a chance it is still
salveable? has this happened before? HELP! I may have lost important video