I ran into this when my marriage to my first wife fell apart. She thought she was bi, but "just never met the right guy" (who was supposed to be me); ten days of marriage (and a fair amount of heterosexual sex — honeymoon period, and all) made her realize that nope, there were no right guys.

And my lesbian friends were, "Could have told you! Remember when you asked us for advice? Oh wait, no, you two just ran off to a JoP and got hitched!" VERY strong "there are no bisexuals, just women who haven't been honest with themselves yet" vibes. This was back in 1990, for what that's worth.