All but 1 villiager vanish

I was mining under the villiage in a mineshaft when my game randomly crashed. When I got back on I came out of the mine & there is only one villiager in the entire villiage. The villiage is fenced off so no zombies can get in. It was night. I was playing on hard so if a villiager was killed by a zombie it would have turned, however there were no zombie villiagers.